For me, the greatest ever is SNES, it developed the NES in a way that many people didn't think was possible. But then the N64 did it to the SNES. In my opinion no other company have made sutch big things for modern gaming like Nintendo. Sure I'm a huge fanboy and have supported Nintendo for all my life.
Sure, there were good games that took the evelution forward on other consoles to, but think about it. What do you think modern gaming would be without Super Mario 64, the game that took the gaming in a new direction.
I would like to say the same thing about the Wii in the future, because I think that motioncontrols are the future and will be the big thing in nextgen consoles, at least in some way.