I forgot one console : What about the Gameboy micro ?

Only if you want to waste your money.

Buy the GBA SP version two bright screen. Don't bother with the DS Lite when you're jsut using GBA games. The cart sticks out. And the unused screen makes it annoying. Model ags-101.

I go DS Lite for the back light to really make the colors pop.

DS Lite.

I'm going to agree with a few others on here and say GBA SP AGS-101. It's backlit, has a bright screen, it's ultra portable, and has great controls. The Micro will cost you an arm and a leg because of it's rarity, and a DS lite, although very nice, has a different screen size and is not Gameboy or Gameboy Color backwards compatible. Buy a 3DS if you don't have one already to play DS games. Just my opinion.

GBA SP AGS101 (backlit)

Hey! The Micro is awesome :P

SP, no doubts.

DS lite is the obvious choice. It plays DS & GBA games, has incredible battery life, and it looks more stylish than the SP imo. Can't go wrong.