Is there a version of RBI for the Gameboy Advanced yet? I'd pick up an advanced in a heartbeat if there was.
Advance dammit, advance. Sorry, pet peeve. :)
I doubt there'll be any releases of any RBI for the GBA, but there is an NES emulator for GBA (http://www.pocketnes.org) that you could use to play RBI, provided you have a flash card and the required hardware.
Nightwulf
Also, you can play the licensed version (under 256K) with another player using a link cable.