I once get banned for asking what's a good game to play on a gba emulator

Well, technically they are illegal, not needing to buy a GBA to play its games. Well, just think on what's good on GBA and play it.

Always Pokщmon.

Harvest moon is also fun \o/

Most if not all card games were good on GBA.

I never really played any card games on the gba besides Yugioh.

I have 2 Yu-Gi-Oh games on GBA and a duel masters game. Even though I was never a fan of duel master, the game was really fun.

emulation is completely legal if you own a hard copy of the game

That is a big if, most emulator users don't.

True, I use that stuff to play gameboy games on my galaxy S2 :3