Any of them up through FFX are decent at a minimum. After that shit gets iffy and often awful.

If you're looking for one of the 2D games, I'd suggest going for VI (the one marketed as III in the US and other places because reasons). The others are good too, that one is just my favorite of the 2D games.

If you want one of the 3D ones, eh, kind of a toss up. I'd say you can't really go wrong with anything from VII through X. VII and IX are my favorites from that group though, for what it's worth.