My favourite FF is, and probably always will be FF7, I've lost count of the number of times I've played it. I'd say X-2 is my second favourite FF although it was way to easy up untill Vegnagun. FF10 is possibly a 3rd cause it got really clever halfway through although it was way too easy most of the time. The only challenging parts were when you couldn't use the aeons for whatever reason or when you don't have Yojimbo. I did prefer the princible of the CTB battle system though.