I agree, I love FM and will always think good FM or "real chiptunes" are more impressive than good sample-based synthesis, because you can't just lean on your sample library. There are a few Genesis trackers out there, including Deflemask[1], vgmmaker (which sadly, the author took down because he got tired of dealing with unappreciative jerks, so you'll have to Google a bit to find a copy), and YMDj [2] (a "native tracker" that runs on the Genesis itself)

[1] http://www.delek.com.ar/deflemask

[2] https://www.youtube.com/watch?v=nTDiPqkoFnc

A little over a year ago, Titan released a demo for the Genesis called Overdrive, and, well, it's fucking amazing, go watch it: https://www.youtube.com/watch?v=iQqJm14sHRY