To be honest, every Gameboy had somethingnwrong with it.
Original-Bulky, used a lot of batteries, no backlight.
Pocket-No backlight
Light- Well, to be honest, the original Gameboy just had a kind of weak library in my opinion. Light as a console is good, but it can't be the best since it was in Japan only and in my opinion, it doesn't count unless you live in Japan.
Color- No backlight and obselete after 3 years.
Advance-No backlight, used batteries. Perfect otherwise, love how it feels in your hands and layout of everything.
SP-Too narrow, no headphone jack on console, had to use special attachment.
Micro- Can't use link cables.
Overall, I think the micro is my favorite since I don't have friends who would play Gameboy with me anymore anyway. Ideally, I would have like a redesign of the original Advance withe a rechargeable battery and backlight. But the micro is just so awesome...