Let's see...
I still have my NES and SNES. NES is temperamental, but I can still get it to work. SNES still fires up right off.
NES:
Mega Man 2-6
Super Mario Bros./Duck Hunt
Mario 2
Mario 3
Guerilla War
Marble Madness
Legend of Zelda
The Adventure of Link
1942
1943
Commando
Ikari Warrior's (I am unsure if I still have these or not. I believe I have 1 and 2, but REALLY unsure bout 3)
R.C. Pro-am (I am unsure if I still have it or not)
Tecmo Bowl
Tecmo Super Bowl
Top Gun
Played but don't own:
Back to the Future
Caveman Games
Contra
Rampart
Tiger Heli
Twin Cobra
Sky Shark
Spy Hunter
Super Sprint
SNES:
U.N. Squadron
Super Mario All Stars
Super Mario World
Super Mario Kart
Super Scope 6
F-Zero (I honestly do not remember if I still have this one or not. I'd have to dig, but ballz to that. At the very least, I've played it quite a bit)
Star Fox
P.T.O. II: Pacific Theater of Operations
Played but don't own:
Desert Strike: Return to the Gulf
A.S.P. Air Strike Patrol
Doom (I played Doom on the SNES to see what the difference was, and that I didn't have the full thing on PC. Was disappointed with music)
Earthworm Jim 1/2
The Hunt for Red October
Mario is Missing
MechWarrior
MechWarrior 3050 (I can't remember WHICH of these two I played, but I know I played one of them if not both)
Micro Machines
Operation Europe: Path to Victory (This game got me started on strategy games, big time)
Pilot Wings (Wish I could of played this one more often, even own it. I found it quite fun)
Star Trek: The Next Generation: Future's Past
Super Battletank: War in the Gulf
Super Star Wars (all 3 of them)
Tom and Jerry
Wing Commander
Wing Commander: The Secret Missions (both I really wish I had purchased

)
Wings 2: Aces High (when I first saw the commercial for Aces High, it instantly made me thing back to this game

)
Rampart
Everything still works.

Well, aside from my NES giving me the 8bit middle finger now and again.

Arcade wise, oh boy, Galaxian, Galaga and Asteroids, definitely. Afterburner, Teenage Mutant Ninja Turtles, Rampart, and so many other's I can no longer remember the names too.
Damn you all!!! Now I wanna pull all that stuff out and set it up. And damn well would, if I had the bloody space to do it.
