I would really love to see the old Final Fantasies (and perhaps some new ones?) on the GBA. My GBA is doing nothing but collecting dust. But if Final Fantasy were to be released, I'd play it all the time! I'd also love to see a Chrono Trigger port.
P.S. Final Fantasy 5 was only released on SNES in Japan.

It never made it to the US except for in the form of a Playstation port, and hasn't come near to seeing the light of day in the UK.