My Top 3:
PS2
PS3
PS1
I've never owned a bad system because I would've not had bought it in the first place if I wasn't gonna build a library for the system.
I've owned so far, Gameboy, Gameboy Colour, Gameboy Advance, Gameboy SP, DS, DS Lite, Nintendo 64, Gamecube, Wii, PS1, PS2, PS3 and PSP.