Redirect me to a thread if there already is one:
30: Doom (Really fun shooter and great for it's time)
29: GTA: San Andreas (Good plot for those who like that, and also for people who just want to cause chaos)
28: Animal Crossing: Wild World (Fun game, you can do a lot of stuff on it and it lasts forever)
27: Tomb Raider 2 (Very challenging, but incredibly fun and good weapons)
26: Airblade (good physics engine and great multiplayer modes)
25: Halo Wars (great for new and veteran RPG's)
24: Crysis 2 (Amazing graphics and solid, down to earth gameplay)
23: Mortal Kombat 9 (gives Mortal Kombat it's name back again after the abysmal DC game)
22: Robot Wars: Arenas of Destruction (Very fun while I was a child and good gameplay)
21: Red Dead Redemption (possibly the best storyline on the list and great gameplay)
20: Portal (risky concept, but paid off immensely in the end. Amazing game)
19: New Super Mario Bros (Really good fun, and a very good challenging game)
18: Fallout 3 (covers all aspects of gameplay, and great karma system)
17: Halo: Reach (average really, but the Forge game mode is absolutely amazing)
16: Pokemon Diamond (loads to do, possibly the last good Pokemon game)
15: The Urbz: Sims in the City (DS Version) (fun challenge and really pleasant to play)
14: Formula 1: 2002 (great for it's time, and exhilarating. Me and my friends would always race each other on it)
13: Crash Bandicoot: Wrath of Cortex (really fun gameplay, but a bit fiddly at times)
12: Castle Crashers (really fun beat em up, hours of gameplay and loads of unlockable characters)
11: Earthbound (really good solid RPG, an enjoyable experience for everyone)
10: Crash Bandicoot 2 (had to be in the top ten because it has my favourite video game character of all time (RIPPER ROO) Also, really fun levels.)
9: Half Life 2 (Very well made game, so much to interact with)
8: Call of Duty (ignoring the people online, this has so much customizing and great graphics and gameplay)
7: Pokemon Firered (10 times better than the original Red, but that was amazing as well)
6: Team Fortress 2 (great generic gameplay on Xbox, loads of customizing on the PC. Fun on both consoles)
5: Mario Kart Wii (Loads of characters, superb power ups, great tracks, love this game)
4: Mortal Kombat 3 (Brutal fatalities, really good combo system, good cast and days of fun)
3: Left 4 Dead (endless amount of possibilites, amazing teamwork builder, loads of fun gamemodes)
2: Star Wars Battlefront 2 (the best 3rd person shooter of all time. Loads of vehicles, useful classes and very well made maps for endless fun)
1: Crash Bandicoot 3: Warped (my favourite game ever. Time trial mode, unlocks, fun bosses and enemies, just awe-inspiring)