Console Wise? Gotta say Nintendo, didn't know anyone back then that didn't have one. Also had more market domination then the PS2 as others said.
Handheld wise gota love the Gameboy. I mean, till the PSP came out Gameboy pretty much was untouchable. Even now the DS still holds close to 70%, and then when you factor in game piracy forget it.
It's just that simple.