I have put 31+, thinking quickly about it...
Pong, 2600, 5200, Microvision, Mattel Football, Racing, Basketball, Soccer, Battlestar Galactica, Baseball, Blip, NES, SuperNintendo, Genesis, Genesis CD, Genesis 32X, Genesis Master System Adapter, Nomad, Game.com, GameGear, Gameboy, Gameboy Color, Gameboy Advance, Gameboy Advance SP, (Nintendo DS in two weeks), Saturn, Dreamcast (5 of them actually), Nintendo 64, Gamecube, Playstation, PSOne, PsOne w LCD, Playstation 2, XBox, NeoGeo Pocket Color, additionally have owned Atari Paddle controller game as well as several other handhelds from the late 70's and early 80's...Oh yeah, Gameboy Player for Gamecube, as wellas Gameboy adapter for SNES...I'm sure there are others, but it's late and that list was off the top of my head...
Now I need to get to bed so I can stay up TOMORROW night for Halo 2...I should stay up now and grade papers and do lesson plans..but oh well...