Best:

Atari 5200 - Big and sexy. (I know...I know)
Sega Master System Model I
Dreamcast
Gamecube - Truth in advertising, I guess.
Game Boy Advance (non SP)

Worst:
SNES model I - Bland. And can somebody explain why I need four fingers to turn the thing on?
Intellivision I - Worst of the woodgrains.
Game Gear
N64