The GBA is more powerful than the Snes, and is capable many things the Snes couldn't even attempt at doing, its just at the moment, Nintendo have been lazy and re-released games I completed 7 years ago, which I don't buy.
I am disappointed with the GBA, but that is because I've played a lot of the titles before, and have them on Snes and in Rom form. But... there are a few games that I enjoy immensly, one, the afore mentioned Golden Sun (they don't make them like that on the next-gen consoles anymore!) Two, F-Zero Maximum Velocity, which is a great, challenging but rewarding game that is an expansion of the Snes version (which I never 'owned')
A new Zelda game is sorely needed (I think Capcom are working on one), or even a new Mario game. Also if you haven't played EarthBound as you are too young/ live in Europe, it is being re-released.