Alright this is gonna hurt a little:
DOS
Monster Bash
Attack of the Mutant Space Bats
Commander Keen (already listed, but it’s fun)
Clyde’s Adventure (surprised no one listed it yet)
Clyde’s Revenge (sequel to the above)
Skyroads
Asteroids (revisioned with semi-3d graphics)
Spit-Wad Willy
Hugo’s House of Horrors I, II, III (no better text-walkabout game, not even Peasant’s Quest)
Jazz Jackrabbit (it’s DOS right? can’t believe i forgot this one)
Elfland (i love smacking birds out of the air with a flash berry)
Chex Quest (my first FPS, and quite possibly the only one i’m good at)
Nintendo
Mario 1, 2, 3 (obviously)
Duckhunt (ditto)
Captain Skyhawk
Donkey Kong Jr.
Joust
Super Nintendo
Mario 4
Mario RPG
Final Fantasy 4, 6
Gundam Wing Endless Dual (yay, anime fighter!!)
G Gundam (yay, more of the same!)
DBZ 1, 2, 3 (ok, now that’s a bit much…)
MegamanX 1, 2 (still need to play 3)
Genesis
Sonic 1, 2, 3, &Knuckles (totally awesome of course)
Golden Axe
Streets of Rage
Columns
Super Hang-On
That’s all for now. Also, I refuse to believe that the Dreamcast is an “old” system, simply because it kicked so much ass, only it did it too prematurely, and no one realized that their asses were being kicked. I mean, seriously, almost-PS2 graphics during the PSone and N64 era? why did no one grab it? It’ll be old when the games become downloadable for the Wii.
Additionally, if anyone likes those old-timey DOS games, i’ve got a website for you: http://www.dosgames.com/
so cool. note that dos games are not emulators, but are free simply because they are really old. And the other games may be obtained through other means, whether legal or not, your choice.