Here is my list of games that need to be ported to GBA badly:
Final Fantasy 6 (FF3 US) - The first Final Fantasy game I played and the only one I enjoyed thoroughly. I feel the only way I can dedicate time to play it through again is if it were portable.
Chrono Trigger - Again, another great Squaresoft RPG that would make a lot of people happy.
Final Fantasy 4 - I heard this one was really good, and again, the only way I'd have time to play it is if it were portable.
Sonic the Hedgehog series (1-3, Sonic CD??) - These were great games, especially #2. I wasn't too impressed with Sonic Advance (I haven't tried Sonic Advance 2 yet). I want the original games! I'm sure if they are creative enough about it, they might be able to fit Sonic CD on a cartridge, too.
While we're at it, Nintendo, how about a brand new Super Mario Bros. 4? No, I'm not talking about Super Mario World, it would be a brand new 2D platformer that's done in the spirit of the originals.
Anyone else have such a list? Let's hear it!