This is going to take a while, starting from upper left:
First row
1. not sure if Nico Bellic (GTA IV)
2. Bard's Tale
3. Space Invaders
4. 1943(?)
5. Silent Hunter(?)
6. Sim City and Settlers
7. Sonic
8. Populous
9. Sid Meier and the rocket is probably for Alpha Centauri
10. Goblins? not sure
Second
1. Ivan from jagged alliance?
2. Spore and Zeno Clash
3. Forgot the name, the game where you build bridges and stuff out of goop.
4. Hitman and Discworld Noire
5. Lemmings and not sure what the others are
6. Painkiller, Legacy of Kaine, Bloodrayne, Army Men and possibly a Dungeon Keeper imp.
7. Max Payne and that chick from the Matrix game/movie.
8. Thief
9. Mirrors Edge
Third (Diverges from the Discworld Noire character)
1. Skaarj from Unreal and UT and Commander Keen.
2. Grim Fandango, Dungeon Keeper and Gothic(?)
3. Upper: Street Fighter, Batman: Arkham Asylum and Manhunt.
Lower: Beyond Good & Evil, Duke Nukem and Redneck Rampage.
4. Bomberman and Gears of War
5. Dead Rising 2, Left 4 Dead, Dead Space and Alone in the Dark(?)
Fourth
1. Upper: Sims (not sure about the animal)
Lower: Final Fantasy 7 and Total War: Shogun, Rome and Empire.
2. Upper: Bully and Call of Juarez.
Lower: Sid Meier's Pirates!
3. Duke Nukem and Serious Sam.
4. Cthulhu, don't remember the next two, pandemonium (?), X-Com, Evil Genius, Day of the Tentacles, ?, Monkey Island, Overlord, Metal Slug, System Shock 2.
5. Upper: Blood Bowl, Blood, Mass Effect and Dragon Age.
Lower: Some adventure game I forgot the name of.
Fifth
1. Alice, Silent Hill, Pacman, ?, Sam and Max (not sure about the characters inside), can't remember the name but know the game and Psychonauts.
2. Fable, Crysis and Full Throttle.
3. Rayman Raving Rabbids, Resident Evil 4 and not sure what the other two are.
4. Devil May Cry and Guilty Gear.
5. Don't know the man but ALLEY CAT!
6. Tetris
7. ? and Postal.
8. Half-Life, Full Throttle and Vice City.
9. Mechwarrior, Abe's Oddysse and Liddle Big Adventure 2.
Sixth
1. ?,?, Dungeon Keeper, Leisure Suit Larry, No One Lives Forever, ?, Hellgate, Witcher.
2. Red Alert 3, ?, ?, ?, Carmageddon, Halo, Starcraft, Far Cry, ?, ?,
Under the truck: Team Fortress 2, Commandos and Metal Gear Solid.
Seventh (a little wider this time)
1. Fallout, Jazz Jackrabbit, Braid, Street Fighter, Guitar Hero (not sure about the guy in the robe) and Discworld.
2. Bioshock, Aliens vs Predator, Quake 3 and Unreal Tournament 3 (could just be both Quake 3)
3. Upper: Earthworm Jim, Dune, Worms, STALKER, Z, Megaman, Crusader, Quake 2.
Lower: Daikatana, Assassins Creed, ?,? and Deus Ex
4. Bladerunner(?) and Star Wars Republic Commando.
5. Command & Conquer and Starcraft Ghost.
Eight
1. Portal, ?Minecraft?, Splinter Cell, Dungeons and Dragons, Ragnarok Online, ?.
2. UP: Gothic, Puzzle Quest, Baldur's Gate 2, Three Vikings(?)
Down: Doom II, Rayman, Planescape Torment, Mortal Kombat, Doom, Doom 3, Space Quest, Severance, Resident Evil 3.
3. Upper: Warcraft 3/World of Warcraft, Soulreaver, Knights of the Old Republic.
Lower: ?, Prince of Persia.
4. Quake, MDK, ?
5. Doom and Diablo
6. Out of This World.
I'll edit in some more in a bit. There's not that many games I don't recognize here.
I probably left out a few small ones, but I'm done for now.