I agree. The FM2 is pretty unnecessary, as it's simply a fully manual exposure camera with a 1/4000 shutter speed. Impressive for it's day, but really doesn't do anything for you or warrant the price. It's well made and all, but most Nikons were well made back then (save for maybe the EM)
a Nikon FG is of poorer quality than the FE/FM series, but it's also got Aperture priority and Program auto-exposure options to go along with Full-Manual. Pretty nice for if you want some dummy modes. (personally, I love shoot in Aperture Priority if I'm not preparing a specific shot, so it's nice to have).
The only caveat with one is that it won't work with non-AI lenses (pre-1977). If you want to shoot these (they're more affordable if that means anything to you), I recommend the FE or FM cameras since they support them well. Don't get the FE2/FM2 in this case, as they will not work with Non-AI lenses, and only really offer you 2 stops of faster max shutter speed and TTL flash in return. Otherwise, same camera and costs more for stuff you don't really need.
Personally, I loved my FE before it became the only one I've known to have the shutter fail (strangely enough, it still works in M90 backup mode), and my 15$ FG has taken it's place very well ever since as my go-to MF Nikon body.