Some of my faves:
Bionic Commando - NES
Marvel Vs. Capcom 2 - Dreamcast (THE game for my friends and I during High School)
Soul Calibur - Dreamcast
Ice Hockey - NES
Madden '95 (I think) - Genesis
NFL 2K - Dreamcast
Final Fantasy 7 - PS1
All Super Mario Bros games except Mario 64 (sorry, I just couldn't get into various Nintendo 64 games) - Nintendo platforms
Double Dragon - NES
Teenage Mutant Ninja Turtles 2 - NES
Contra - NES
World of Warcraft - PC
Legend of Zelda - NES
Duke Nukem - PC
DOOM - PC
Wii Sports - Wii
Man, there's just too many to list...I was a hardcore gamer from the time I was a little kid (27 now) and have owned nearly every system. Neo Geo one of the few myself and my closest friend have not been able to/wanted to obtain. I actually find that the further gaming gets technology-wise, the faster I get bored gaming. There's just something about 2D that works IMHO. I've been playing the new Super Mario Brothers for Wii and loved it...but the Mario Galaxy 2 game, while very good, just didn't suck me in.
Of all the games I've owned...World of Warcraft, Marvel Vs. Capcom 2, and Soul Calibur were probably my 3 favorite games, but I could be forgetting some. Oddly enough, fighting games are usually the ones I tire of the fastest. Those two were just amazing.