Sega Genesis, N64, PS2, PS3, a pair of joysticks that you plug into the TV with old school games programmed into them, and my PC, Gameboy Color (if you will count it), and a Gameboy Advance SP (again, if you will count it).
NES, Nintendo 64, SNES, All gameboys, Atari, Dreamcast, That old Sega thing..., Commodore.... PC, PS2, PS1 Eeh... Wii.... A laptop that can be used for games...
Somewhat uncommon NES 2 (toploading version released to go with the SNES), actual SNES, N64, Gamecube, Wii, GBA SP, fat DS. I used to have the original GBA, but I tripped while it was in my pocket and landed on it. Even for a lightweight person, that does serious damage when the screen is on the outside (thankfully we have folding handhelds now )
Summary: I can play pretty much any Nintendo game on at least one system, other than Virtual Boy games