The Best RPG...

[Sarisa]

GBA: Tales of Phantasia, though it was close between this and Pokemon Emerald. Honorable mention to FFV as well.

GBC: Pokemon Crystal. I think it's the only GBC game I've played so no contest really, and I technically played it on my GBA anyway.

PSX: Final Fantasy IX as I think it's the only PSX game I actually finished, though I nearly completed several others (which were also mostly FF titles).

PS2: This is a tie between FFX and Tales of the Abyss as I love them both equally. So many good titles to pick from here.

PS3: Tales of Xillia. The only other PS3 game I completed was Tales of Graces f, but I never did finish the future arc so I went with Xillia.

Gamecube: Tales of Symphonia. Only other games I played for it were SSBM and some Naruto games, but those were mostly just for vs mode and aren't really RPGs anyway.

PC: Eternal Senia as it's the only PC RPG I've played outside of Pokemon Reborn which is a fangame so I don't know if it counts.