[Complex Simplicity]

pokemon yellow
super mario land 2
sonic adventure
Championship manager 01/02
wario land 1

[foxo]

Really difficult question. In no particular order:

Deus Ex (PC)
Halo: Combat Evolved (Xbox)
Red Dead Redemption (Xbox 360)
Planetside (PC)
Elder Scrolls: Skyrim (Xbox 360: still not completed it but I've not been this impressed by a game in years.)

Honourable mentions: Quake III Arena, Unreal Tournament, Doom II, Half Life, Tetris, Shenmue I and II, Fallout 3, Fable, Mass Effect 2.

[lubus]

a pretty rubbish selection so far

heres mine

Half Life 2
Starcraft 2
WOW
CS Source
DOOM 3

Games I really liked: Deus Ex Human Revolutions, Cossacks, Red Alert.

[Gazmatron]

Final Fantasy 10
Zelda: OOT
Final Fantasy 9
Pro Evo 3
GTA San Andreas

[Apa]

In no particular order:
Spyro (pre-2003)
Crash Bandicoot (again, pre-2003)
Wow :P
Pokemon (red/blue)
The Sims 2

[Aijin]

Heh, this is hard...

1. Final Fantasy X
2. Metal Gear Solid 2
3. Lost Odyssey
4. Dynasty Warriors 4
5. Soul Calibur 4

[the mad scientist]

Crash Bandicoot 3 Warped
Pokemon blue
Professor layton and the curious village
Professor layton pandora's box
Professor leyton and the unwound future

Just got the 4th Professor leyton for christmas

[alishachuhan]

My all time favourite games are
Call of duty 3
Dx ball
Modran walfare 3
Need for speed world
Solitaire

[Dat Guy]

Fahrenheit
Mass Effect and ME2
Resident Evil 4
Halo trilogy
Neverwinter Nights

C&C: Red Alert 2 would be my honourable mention

[A7iif]

1.Uncharted 2
2.MW2
3.MW3
4.Uncharted 3
5.Assassin creed II
6.LittleBigPlanet

[Hester_23]

Metal Gear Solid
GTA Vice City
Dead Space
Batman Arkham Asylum
Streets Of Rage

[mistermeowingtons]

In no particular order;

Half Life 2
Final Fantasy VIII
Pokemon Blue
Harvest Moon: Back to Nature
Tomb Raider

[Picnic1]

Sticking to 3D games:

1 Uncharted : Drake's Fortune (I think that they got it best first time- after that they tried too hard to make stealth adventure games)
2 Banjo Kazooie
3 Jet Set Radio Future
4 Metroid Prime
5 Rage

Or replace Metroid Prime with Crash Team Racing.

[TooEasy123]

SOCOM: U.S. Navy SEALs Fireteam Bravo 2 (PSP)
Tony Hawks Pro Skater (PS1)
Hitman 2 (PS2)
GTA: San Andreas (PS2)
GTA: Liberty City Stories (PSP)

[illusionz]

In order of the most fun I've had playing them

Medal of Honor Allied Assault: Spearhead - anyone who used to play it listen to this and it bring back memories!
Call of Duty 2
World of Warcraft
Call of Duty: United Offensive
Team Fortress 2

Honorable mention to Skyrim and Red Alert 2, but single player games have never given me the hours of playability that playing online with friends does. However, if I'm honest the levels of fun I've had playing these games is largely down to the people I've met and played with. Strange to think where they are in their lives now.

[Fusion]

Tough question

CoD4 MW1 (online)
GoW1 (online)
Resident Evil 4
Tomb Raider 2
Pro Evo 2

[When you see it...]

I don't really like categorising art in this way, but whatever, I'll play:
Final Fantasy XII
Pokemon G/S/C
Persona 3
Uncharted 2
Bioshock
I like loads more, but they are five that come to mind...
EDIT:
I know you said 5, but I just have to mention Chrono Trigger... and Final Fanasy VII... and any FIFA game... and Goldeneye 64. Okay, I'm done. Also, someone mentioned Valkyria Chronicles which I never really got into, but really enjoyed and will probably play again once exams are over...
Finally, does anyone else think that Sonic Rush is an underrated game?

[idiris]

battlefield 3
modern warfare 3
resistance 3
need for speed the run
fifa 12

[Hazz1]

Tekken 3
Super Mario (gba version)
fifa 10
Halo
Ridge Racer

[GottaLovePhysics! :)]

Half Life 2
Grim Fandango
Rayman 2
Worms
Simpsons hit and run