Yep, it never got a PC release, and even if the devs bundled it with an emulator... PS2 emulation isn't exactly great and it's really system intensive.
If you have a GC or PS2 though, Summoner 2 is DEFINITELY worth getting.
If you have a decent pc (quad core), ps2 emulation is great. I have replayed Final Fantasy 10 last year without any hitch. And yes the better your machine, the better options you can use.