Original Call of Duty - I dont know what it was, it just sorta sparked something in me as a WWII history lover.
Doom I, II, TNT, Plutonium - Old school awsome
FEAR - Sweet Jesbus did it have a good single player campaign
Half Life 2 - Also an epic single player
Portal - So awsome... Just so awsome
Hitman Blood Money - Played though every mission so many times just for fun
Starcraft - More old school awsome
Test Drive: Unlimited - Closest thing to an MMO I will every play
Company of Heroes - What im currently playing on LAN with my roomate now.
Honorable mentions:
Navy Field
Red Orchestra
CoD: United Offensive - For the giant multiplayerness
The best game:
Team Fortress 2 (Ridiculously fun)
Half Life 2 + Episode 1 and 2
FEAR (Never had a game that gave me chills before.)
Oblivion (BEST RPG game I've ever played)
Diablo 2
UT2k4 (Onslaught only)
Half Life (One of few FPS I acutally finished.)
WoW (Would be my #1 if it did't destroyed my previous relationship of 7 years)
The rest of the game was between good and Horrible.
Not sure of the best games I've ever played so I'll mention 5 of the greatest games I ever played only thing is they needed to do something revolutionary for me.
1.Smash Brothers 64
2.Baulder's Gate II
3.Zelda: Ocarina of Time
4.Elder Scrolls 3: Morrowind
5.Counter-Strike: Source
Total Annihilation
Warcraft 2
World of Warcraft
Starcraft
Tribes(!)
Chronicles of Riddick
Call of Duty
Doom 1 / 2
Quake 1 / 2
and been liking Hellgate: London (but who ran the QA department?!)
If I had to choose ONLY one game as the best ever for me, then it must be...
Diablo
It was the game that hooked me on PC gaming. It also introduced me to multi-player gaming. I spent countless late-night hours on Battle.net with friends from work as we battled Diablo and his evil minions. Those were some great times.
My current best games are Call of Duty 4 and Dreamfall. Of course, this list changes every year.
Guitar Hero (All)
Audio Surf (Addictive little Game)
The Burnout Series
Serious Sam
Civilization Series
SimCity Series (Except for Societies...)
Portal
Many Many More
Thanks for all the replies. I did forget to mention Hitman: Blood Money. When I start playing it I can't stop until I get so pissed that the AI has psychic abilities.
Arcade:
AfterBurner
Bad Dudes
TMNT 2
Mortal Kombat
Cruis'n USA (Dual)
PC:
Warcraft 2
Duke Nukem 3D
C&C Red Alert
Urban Terror
Console:
Super Mario Bros. (NES)
R.B.I. (NES)
Street Fighter 2 (SNES)
Super Mario Kart (SNES)
TMNT 2 (SNES)
Star Trek: Starfleet Academy (SNES)
GTA: Vice City (PS2)
GTA: San Andreas (PS2)
GH3 (PS3)