Mount & Blade: Warband. I just love taking part in and commanding huge battles. Even the sieges (which are tough at best and annoying at worst, due to collision and AI issues) give me a thrill. Very few games portray battles in a similar way, and none of them handle melee and ranged combat in as interesting a manner. And oh, the mods! So many great modules. You can change the game to be set in feudal Japan, or the ancient world, or WWII, or various medieval eras, the Wild West, Viking-era, Napoleonic wars. Or various fantasy worlds ranging from original settings, to Middle-Earth, Westeros, Star Wars, Warhammer, and maybe some others. I can't wait to see what Bannerlord (the next sequel) is going to be like.

Hmm, it's hard to pick one. I'll say super mario bros original NES version. I played it so much as a kid and still to this day it's instantly fun to play.

Several games came up to my mind, but I think Baldur's Gate 2 is my favorite. I enjoy good story and characters, so I used to enjoy playing JRPG type games. But exp farming gets boring, and a lot JRPG games force you level up to proceed (though i really enjoy Romancing SaGa 2). So I turn to games that you can find ways to work around a difficult fight, or just get prepared with different ways other than exp farming. Old Fallout series are fun too, but BG2 is my favorite.

Dark Souls or Fallout 2. Fallout 2 was what first got me into RPG games. Great story and a really bleak world.

Quake Live - best 1v1 competitive FPS game

Persona 3. I love the history how they use all the elements of the game to tell you that its all about the death and triying to find something to live even in the lowest point of your life, and it was the game that made start learning english by myself so its linked to me in a very emotional way.

Zelda - A Link to the Past for the SNES. Childhood memories :3

Tooo many ;) Gaming since Atari in '78 lol (AMIGA fan here)
BF 3/4/1
ME ALL series & Andromeda
DA ALL series
PES since 2005
Arcade Games -> like Seraph :D
NFS ALL series
Now Forza on WinX
ZEN 8/16 4GHz + 16GB (soon 32GB & M.2 1TB 3200/1600) + Furyx (soon VEGA RX but 16GB HBM2 ver. when avaible AIBs) + SB-Z 5.1

Deus Ex - the graphics haven't aged well, but the gameplay and storyline are still the best of any game I've played!

Grim Fandango, classic adventure with an expansive original story, amazing art style, excellent voice acting, beautiful music, good dialog, (mostly) good puzzles, and extremely memorable characters!

The Longest Journey series always stood out to me as something fun to return to, though Grim Fandango was always right up there with it in the nostalgia rankings.

Thanks for the chance!

Morrowind. It was so big, so full of good stuff, I think it was my first fully open world.
Also Blackwell series. I just love the story.

Well well, lots of good games here ;)
I already know and tried most of them !
To be honest, I'm not really into Sports or Racing games ( all but the NFS games ) but I am so in the Souls serie and RPGs/MMOs.
My favorite game is and will always be Final Fantasy 7 ! The vast world, musics, every crazy mechanics ( Cait Sith, the Gold Saucer ), stylish characters, THE OMFG AMAZING ZOLOM and ... well ... just everything in this game is amazingly perfect to me :D

cRPG - Fallout 2
RPG - Deus Ex and Dark Souls
Strategy - Alpha Centauri
FPS - Doom II
Platformer - Super Metroid
Action Adventure - A link to the past
Point & Click - Gabriel Knight: Sins of the fathers
Sidescroller - Contra

I read what you wrote and i still gotta say Thank you very much! As for games my most played is dota 2, but my favorite game to date i would have to say is Final Fantasy 12 for the ps2. its a game that i loved and spent countless hours playing. Even though i havent played in years, i still have all the places and story and characters stuck in my mind. I sure hope they bring a remastered edition to pc.! ^_^ !

Final Fantasy VII - There was really nothing else like it at the time for RPGs.

i could not pick a single one. There are several i love for different reasons:
X-COM: UFO Defence. For how it integrated a pretty good on its own turn based tactics game with a strategy overlay. The new series is also good, but it lost complexity compared to the original.
Deux Ex: for all the options it gave you. There is no optimal path to the end, choose however you want to play and you will find a way.
Fall Out New Vegas: for its setting. A lot of games have done the post-apocalypse scenario, but in this one you get to see what happens next, when people begin to create new nations in the wasteland.
Myth I and Myth II: Soulblighter: excellent real time tactics (it is not a RTS) with a great story in the single player campaign.

well, i think it will be either Paradox game, because of their detail and deep strategy level mechanic of their game

I have a lot of favorite games. But my most favorite two are Vietcong (which is not on steam and sadly not much people are aware of this gem) and The Witcher (Franchise/Series). I have a favorite or two in each one out of many genres, but I will not bother you with it. Vietcong and The Witcher are good enough. ;P

Chrono Trigger (best old school JRPG for characters, visuals, music, one of the best for gameplay, solid story) or Shovel Knight (just an amazing action-adventure platformer all-around).

dark souls because i am never bored of it

I don't know, my favorite probably is (was) Tanarus. It's been gone for a long time now, but it was such a damn great online game that nothing else has came close to being like. I miss it, especially Phoenix Wars and Force Wars.

Need For Speed: Porsche
Because you could have every porsche car and drive them. Also you could have more than 80 cars in garage.

Such a difficult question...
Well. judging by playtime, my favorite game is Dota2, I love teamplay and competition with other players.