For a handheld, yeah it's good. If I were on a plane or a bus... or I wanted to play SF and I was away from a home console or my computer it would be ok.
But as long as you're in front of the computer or your DC, there are much better Street Fighter games that you could be playing.
Of course! that's a no brainer but that also defeats the purpose of a GBA.
Do think people are actually downloading GBA games because they want to play them on their pc or because they don't want to pay for them? I hope it's not the latter because that would be sad, especially for a handheld.