....literally every final fantasy from 3-8 and soon 9 is on Steam right now plus if you wanna go further the entire 13 saga and Type-0s there
http://store.steampowered.com/search...=Final+Fantasy
you might get lucky and they release tactics...which is actually on Cell Phones so may get a steam release
Breath of Fire...yeah might not wanna hold your breath on an official PC release of that but if you have a PS3 you could connect that to your monitor and buy 4 but that's the best we could do
Otherwise if you actually own a physical copy of said game you can actually rip your disc and use an emulator on it there is NOTHING illegal about that