Burger Time seems like it could be a fun one to tackle, especially with a defined version! I might work on a 3dn version of it once I am done with Gradius, although that could be a while off yet. The simpler games are certainly easier to make, and a change of pace after a more complex project could be nice!
It's also nice to see someone so passionate about the emulator, it really is a cool bit of software, and making 3dn files can be as much fun as playing the games sometimes!