How do you boost your moral to finish a game?

It's a bit unclear from your post if you're enjoying the game or not.
I myself, for example, have a problem where I feel I need to finish every game I start, even if I don't enjoy it. And it has wasted me many many hours.
But I also have a problem similar to yours - where no matter how much I enjoy a game, if I start playing a different game while still playing it, suddenly the game I was playing becomes meh... and I don't want to play it anymore.

For each of these I found a solution that works for me:

1. I never start playing a new game. Instead I "try" games. I allot myself specific time frame (2 hours for example), and after playing 2 hours I stop, and befor continuing ask myself: Do I really like this game? Or am I still not sure?
   Because my main issue was, allways telling myself - Maybe it's just slow at the beginning, maybe it will pick up...
   So unless I really like a game, I stop playing and move on to something else.
   God knows my backlog is big enough...
2. I never ever start playing a new game while I'm in the middle of playing another game.
   If there is a different game (even one that just released), I put it in my backlog (it can be #1 there as far as I'm concerned), and I don't touch it until I'm finished with the previous game.
   For example, I won Kingdom Come: Deliverence a few months ago, and really wanted to try it out because it's an AAA game, and was supposed to be really good (Spoiler Alert: It's awesome!). But I left it in my backlog, until I finished whatever I was playing (a couple of point&click adventure games). And when I finished playing the other games, only then started playing KC:D.

Hope this helps...

If the game doesn't do that for you...drop it like it's hot. You play games to have fun, not to finish boring chores ;)

Subnautica and Return of the Obra Dinn, Alien:Isolation, Soma, Exapunks, The Beginner's Guide, The Flame in the Flood, Gunpoint, Invisible Inc, Portal 1&2, The Talos Principle and The Way all easily carried me all the way to the end...

Put 2 or 3 games in rotation but don't wait to get bored with the first to move on to the next or you might never pick it up again. Rotate every couple of days. And rotate long (20+ hrs to beat) and short games. As soon as you get one done, replace it.
And if you're not having fun, just drop the game.

If a game doesn't manage to capture my attention, I just put it on the waiting pile, to maybe revisit it in the future (probably not). But I have a problem with games I like, but get stuck in at some point. For example I've been playing Pillars of Eternity (warning, light spoilers ahead) for 40+ hours and then there was some big battle where my past choices and actions mattered and I lost that battle in a few attempts and I was sort of stuck because of my quest choices in the past (not enough allies) so I put the game aside. I really like it and I'd like to finish it but I'm not sure if it's even possible at this point and I don't want to start from scratch.

only good games. good story will intrigue me to resumr play hehe.

easy to say... achievments xD

If I stop with a game it's pretty hard to nearly impossible to ever continue with it

Wow, I wouldn't expect such a huge variety of approaches to this question that different people have.

I'll answer it very directly since I'm a person who likes finishing their games and usually intends finishing everything they start playing. Sticking just to one game wouldn't make any sense for me since just like you I love many different genres and each day I want to be able to choose something to play based on my mood, time-constraints, etc. What I do is that I just have an "unfinished game limit" set for myself ("unfinished" being used here in the same sense as on BLAEO - from that the game can only be moved to beaten, completed or occasionally to won't play). I changed the specific value over time based on my feelings about it, but 20 games is something that works well for me. When I'm below the limit I'm free to start any new game I want, but obviously I usually try to choose something different from the games I already have started, so that I still have a good choice variety when the limit is reached. The "unfinished games" category in my Steam library is the only one I have uncollapsed all the time, so I don't have to look at other tempting titles every time when I launch Steam ;)

Hm, interesting topic. I actually experienced something like that in the past few days. I started playing Fallout 4 (bought it for that occasion), got to that first side activity where you need to build a settlement for Preston Garvey & the crew, fiddled around for a bit before realizing 'wait, what does building stuff have to do anything with a Fallout game, this is boring" and dropped it right there. Same with Yakuza 0. Great game but shoddy and outdated controls made me drop it after playing less than an hour. I don't think I'll ever go back to them. I imagine I get less tolerant with age and don't have as much patience to push myself through boring stuff before I get to enjoy the content. I guess it all depends on a game and how these "filler sections" are presented. But to answer your question, if I can tell that I'm already past the point of doing 60% of the game (be it a story or whatever), I might as well push myself and finish the rest

Taking some beer!!! :)

Well...

Do I think the game could get better (good reviews, heard a friend praising it, etc...) ?

Yes -> rush the level\quest\whatever, if it doesn't get better I just give up
No -> well, I'm supposed to have fun, so... uninstall

maybe I'll give it a second chance, but there is no reason to play it without having fun, it's a videogame, not chores

Well, play GOOD games that has a story that really captures you, or fun combat or interesting characters. Another motivation could be Steam achievements (not that they matter much but still).

I like to beat my games, I'm just not particularly minding jumping between different games in the meanwhile. Some games I've taken over 5 years to beat, and honestly, that's fine with me. I find, even with games I love playing, if I spend 40+ hours only playing them, I resent them a little, and the enjoyment isn't there. But if I come back to them every few months I still appreciate them by the time I'm done. And yes I've found that a site like backlogs assassin's is also great at keeping you motivated to keep playing games, you just have to get in the habit of organising your lists and posting your progress. That in itself becomes motivation.

I have the same problem. I start every game doing all quests, talking to all NPCs and checking all corners. Towards the end, I feel like all games become a chore these days and can't help but think that I should start playing something new to get that novelty feeling back. I used to do that a lot and let me tell you, this approach doesn't work. You just end with a bunch of half-finished games that you know deep down you won't ever finish.

Only 2 things work for me:

1. rushing to the end as soon as I start getting these feelings
2. adding consequences to not finishing a game (the reason I like these pay rules in groups).

They're not perfect solutions by any means, but they work for me. ¯\_(ツ)_/¯

I would not do it for bad games, but for good games, I tell myself that I can't remove it until I've beaten it (so it takes up valuable disk space) and I also keep a list of games I beat, and it's somewhat satisfying to see it grow.

bump c:

no disk space :) it is the best motivation for me, I'm trying not to uninstall unfinished games so when I want to install a new one and see this prompt I have to finish another one (although those small indie games destroy my system sometimes;)

I just do a bit of research about the game I'm planning to play: look at the reviews (mainly negative ones to see any red flags), take a look at how long the game is, and see that "length / my love of the genre" ratio is acceptable, maybe look at gameplay if the game is really old.
Still, I do find myself frustrated sometimes, but very rarely I quit the game. Generally a couple of days break usually helps.

Same problem, but I often do finish the games later on.

Set a reasonable goal to complete x amount of games per month and play games that are fun. Also, take short breaks after 2-3 hours of playtime to avoid fatigue.

If you are stuck on the game, read a guide or watch a playthrough on You Tube.

it's simple, if you lost the interest to continue playing the game = it's a bad game for your taste, stop playing it and don't waste more your time.

anyway this is very habitual in this "modern" era with all that AAA games that only care about graphics and ultra good cinematics, they forget about the gameplay and the history.

do you want my advice???

if you like RPG games do the next:

1-download a PS2 emulator
2-Download the game called Suikoden V
3-star playing it and after around 60 hours, start complaining to me on how you have been disconnected from your friends, mobile phone and all your "daily obligations" for play this game until the finish thanks to the history "plot".

I think it's time for you to filter the games you play. With time, you'll not play your games as before, some genres you loved before will not be interesting to you anymore. OR if you love the genre but can't finish the game - you don't need motivation for that, just skip it. Good game (for you) will be finished, no matter what. Don't lose time on those you can't finish, spend that time elsewhere.

i really miss the old days...

silent hill
koudelka
suikoden IV and V
tales of abyss
resident evil games
time splitter future perfect
siphon filter
diablo 2
guild wars
final fantasy tactics
legend of dragoon
chrono cross
......
.........
............

the real gamers want that old times where the history and gameplay was the priority over DLCs and just graphics and cinematics!!!!!

I just don't. If I really like a game I want to play it, I have to force myself to stop to go to bed, work etc. And I feel sorry when it's finished. If I don't want to play it, it's not the right game for me. With all the bundles, discounts and trading stuff we can all have lots of games. So don't force yourself to do things you don't want in your free time. THAT's a waste of time. Just move on to the next one untill you find one that keeps you interested.

Maybe one tip. Don't buy games full price. Spending a lot of money and only playing it for a short time gives a bad feeling. Just make sure your back log is long enough to have something to play until the game you really want now is dirt cheap or gets bundled. That way it will be way easier to stop playing it when you don't like it. We all "must do" a lot but forcing yourself to finish a game you don't like is definitely not one of those things. It's your free time! Do whatever you like without feeling quilty.

I think the real question is why you need the motivation.

Are you not enjoying the game?

If not, don't keep playing it. I spent a lot of time playing GTA IV because everyone said that it was great before I realized that I wasn't enjoying it, wasn't having fun, and no amount of praise from others would make it worth spending my time on a game I didn't enjoy.

Are you stuck?

This has happened to me with a few games. If the game is too difficult, or too challenging, maybe it's worth turning down the difficulty or looking up guides so you can get through it.

Are you getting distracted by the next new thing?

This is a difficult one, and really comes down to willpower. I'm constantly being distracted by the next new thing. Right now I've got a bunch of games that I am dying to play, because each new game is full of wonder and possibilities and I want to experience them all. But I tell myself that I have to finish the first game before I start on the next. So I make a priority list: first finish X, then I can start Y, after Y, I can move on to Z. Thus the desire to play the next game helps motivate me to finish the current game.