Took me a little bit to think of all the systems I have owned. Most of these (minus a few) I still own.
Mattel Intellivision
Sega Master System
Sega Genesis
Sega Game Gear
Sega Dreamcast
Nintendo Entertainment System
Nintendo Entertainment System 101
Nintendo Gameboy
Super Nintendo Entertainment System
Nintendo Gameboy Color
Nintendo 64
Nintendo Gameboy Advance
Nintendo Gamecube
Nintendo DS
Sony Playstation
Sony Playstation 2
Sony Playstation 3
Sony Playstation Portable
Microsoft Xbox 360
Mattel Intellivision
Sega Master System
Sega Genesis
Sega Game Gear
Sega Dreamcast
Nintendo Entertainment System
Nintendo Entertainment System 101
Nintendo Gameboy
Super Nintendo Entertainment System
Nintendo Gameboy Color
Nintendo 64
Nintendo Gameboy Advance
Nintendo Gamecube
Nintendo DS
Sony Playstation
Sony Playstation 2
Sony Playstation 3
Sony Playstation Portable
Microsoft Xbox 360