Single player games in your Steam library that you're not able to finish

90% of them.

"Deus Ex Human revolution - boring storyline and setting, gameplay is too repetitive."

Thats an interesting view on it, most people love the setting/story and the gameplay is more varied then most fps I think...

Dead island and bioshock infinite.

Deus Ex Human revolution - boring storyline and setting, gameplay is too repetitive. This was an Amazing game... damn I beat it twice in a row.
Just Cause 2 - bad storyline, bad driving engine As long as you don't try to 100% the game it's not that long...

Devil May Cry 4, only because it keeps crashing, and I was on chapter 10 I think :(
Good game though.

Super Hexagon: the last level is simply too much for me

Out of the games I actually bothered beginning, only Saints Row II and Skyrim.
SR2 because I can't get the fan-made patch running and just stopped bothering, really. Skyrim... well, every once in a while, I start a new character, play until level 30, get bored and quit it again. Never even got to half of the main story. (And yes, I have lots of mods for it already)

Sideway - boring level design. Cool concept.

Hard Reset - I don't know what's wrong with this game. Everything is awesome. I am just taking forever to finish it.

Batman: AA - Everyone is so hyped for this game and its combat system but for me the controls were bad, the camera was too zoomed in(walking around tight corridors with a low fov isn't enjoyable for me) and the combat was like a dumbed down version of the one in The Path of Neo. I tried to like it. The whole batvision thing is annoying to use, the riddles are not fun to solve, jumping around feels clumsy... No.

Serious Sam 3: BFE - Love old Sam games. This game didn't feel like old Sam games at all. I heard it gets more old school later on and I plan on playing it again but right now I really don't feel like playing it.

Dark Souls - I like it. I am too spooked to keep going. The places I need to go to are too scary and I'm a pussy. Not finishing it.

I took a look at my library and got depresed after realizing I'm stuck at the final boss in a bunch of games. I also abandoned some games after just a few hours, my backlog only gets bigger. I haven't even installed GTA IV and Saints Row 2, and they have been waiting me for quite some time.

Because they were boring? None.

Because they are too awesome to finish quickly? Skyrim... every time I tried making a bee line to the next main quest dungeon I either got sidetracked somehow or took a wrong turn and THEN got sidetracked somehow. There's just soooooo much to do. O_o
I'll complete it eventually though. :D

I also got stuck in Darksiders, but because I could not beat one of the monsters at one point in the story. I should actually try to reload it and see if I could do it now. I would like to finish it before getting into the sequel.

Dark Souls - The controls are clunky and the camera is awful. Also had some issues with GFWL at one point. So I quit that.
Enslaved: Odyssey to the West - I just couldn't get that into it, and dropped it due to the amount of other games I was playing at the time.
Fable: The Lost Chapters - Camera and controls were annoying, so I stopped. I may go back to it, but I've completed it in the past before.

There's a ton others, but I mostly didn't finish them due to already beating them on the 360 a few years ago.

Electronic SUper Joy - i hate platformers but i bought fot the FANTASTIC soundtrack, cant say im disapointed

KOTOR - lost my savegame
Bad Hotel - it's really bad

Max Payne 3. Spent 6 hours on it, for some reason some files went corrupt making it so I can't even launch the game, so I just uninstalled it and Rockstar games doesn't support steam cloud. So fuck it, I ain't gonna install it again

Shadow warrior classic, 3hard5me

Clive Barker's Jericho.. can't get past the first QTE -.-

Borderlands 2. It was really hard and I didn't want to go multiplayer, result = I kept dying and ran out of money, and now I can't buy ammo anymore. (Well it's not like I really spent months in it, only 7 hours) I guess I'll try it again sometime.

Skyrim - Self explanatory. Repetitive gameplay, storyline is horrible, and the graphics are equivalent to plastic surgery when comparing it to the previous game.
Fallout 2 - While technically not in my library, I own it on GOG, I have played it but not finished it. I get up to the oil rig, and the bugs... THE BUGS.
Just Cause(1) - It's too primitive and unfamiliar to Just Cause 2, which I have played.
Age of Empires - Yeah, it's just not very fun for me. Too much time is required to be invested, which I can't be bothered to invest.

Just a few out of the game's I've actually started...

Alan Wake - Already beat it 3-4 times on the Xbox. I'll get all of the achievements someday but I just can't sit through it again right now.

Skyrim - See Alan Wake.

Just Cause 2 - Gameplay is pretty fun, but that story... ugh.

Deadly Premonition - Interesting game, but too buggy. Long loading screens, crashing. Maybe someday.

Darksiders & DmC - Too boring, not a huge hack n' slash fan but they're fun in small doses.

Blocks That Matter & F.E.A.R 3 (Boring)

FTL (Too hard)- I keep on playing but can't beat it on Normal

Bioshock Infinite

Batman AO . . . I got into it hit the bug where I was caught in a room and was like done. . . Also the game felt I uno empty, I'm hoping AK does better.

The Cave. . . I got into it beat a few missions and then just didn't want to play anymore.

Dungeon Defenders - loooooved it but the new stuff that retroactively made some achievements harder and also the market kinda really ruined the game for me. Plus the community started to suck . . or many of the people in it started to troll the game I uno. Most hours I've put into a game. 378 hrs on record

Morrowind, the game is endless :O

During the last few months:

Angvik - No plot and the gameplay is very boring. Couldn't stand it for more than 10 minutes.

Krunch - This one is pretty cool but I had a feeling it's more of a "challenge levels" type of game than story driven gameplay. It's not bad but didn't interest me enough to finish.

Rochard: Hard Times DLC - I finished Rochard and enjoyed it but this DLC is boring as hell. I hate challenge levels in most games.

Vessel - Pretty good puzzle platform game but right now I don't want to play such games. I got bored with it pretty quickly. But if you like puzzle games then go for it, you'll probably love it.

Snapshot - It has pretty good concept but controlling the protagonist is terrible. I played a while but decided to stop at some point. It's not bad, just could have been better.

Offspring Fling! - A puzzle platform game. Bored me very quickly. Not bad, just boring.

Braid - Pretty challenging puzzle platform game. I'm not in the mood for such games but if you like puzzle games then go for it, you'll love it.

Puddle - I finished a few chapters. It's a pretty cool game but gets harder towards the end. I don't know why I didn't finish it. But I don't feel like going back to it.

Starseed Pilgrim - Very boring game. I don't even know what it's about to be honest. Weird one and not in a good way.

Cargo Commander - Very boring platform game with randomly generated levels (I think).

Continue?9876543210 - Boring and tideous. A mix of genres. Didn't like it at all.

Blocks That Matter - Pretty neat puzzle game but it bored me quickly.

Slip - Super Meat Boy meets VVVVVV. Gets very hard pretty fast. I'm not in the mood for such a hardcore action right now but it's not bad.

Ancients Of Ooga - The first game of that developer was Cloning Clyde and I loved it. This one is very boring though. Takes a lot of things from Cloning Clyde plus introduced a few new ones and I have a feeling they tried to incorporate too much into this game. It's getting boring pretty quickly. I tried to finish it but I couldn't. Too boring.

8-Bit Boy - It's actually a good game. But after beating all levels it turned out I have to collect all special coins in order to visit the last boss. I hate such shenanigans. I have no intention of going through half of the levels again and look for those coins.

Harry Potter And The Goblet Of Fire - I finished the first three games from the series and I loved them. But this one is an abomination. Hell, even though I tried to finish it but the more you play the more shields you have to collect in order to unlock new levels. I finished around 3/4 of the game and decided it was enough for me. There's not a single good thing in this part of the series. It's tideous, boring and there are no settings whatsoever so I was stuck with 640x480 (or 800x600) resolution for the whole time. And I went through some hoops to get it cause you can't get it in stores no more so I had to buy it at an auction. I'll say this: Fuck this game.

Almost every game in my library.
Exceptions:
Bastion
Blades of Time
Burnout Paradise
Devil May Cry 4
Dust: An Elysian Tail
Fortix
Faerie Solitaire
Half-Life 2
Machinarium
Portal
Portal 2

Although I finished at least half of these before having them on Steam.