Well, there's GBA emu's there but the most promising one I'd have to say seems like GPAdvance. Right now it runs some demo's and homebrew (I've heard that maybe one or two commercial games run or atleast get to the main menu so the best option is wait for now ) without sound but the first releases showed MODE 4 in atleast 3x normal GBA speed but there's not a final release of it yet... There's also Chui's port of VBA I think it can load almost any game < 4MB. using SDL but it's slow.
you can play dr. driller2, international Karate advance and a boring soccer game with gpadvance.
but the latest version of gpadvance dosn't run realy good with them. it's better to use an older version like ver. 1.48 or what was it? i forget it. sorry.
with the latest version they are running a many slower but there aren't so much graphic problems.
i tried too guilty gear x and wario4. there are running. you can wath the intro but when you are in the game the emu is all the time loading. a bit too long.
1frame and then he is loading again 1 min. so you can't play games like this.
they are 8mb big and the games which are running (dr driller2....) are just 4mb small. maybe someone can find other games with 4mb.
that's all for now