I can't really decide between
LA and
OoS. I've played
OoA as well, but it's more of a nostalgia thing. I had the other two and played them a LOT before I ever got my hands on Ages. (Although looking back on it it only may have been a year, maybe less. Time goes by so slowly when you're young...)
I guess I also preferred the Seasons mechanic over the Ages one, and LOVED exploring Subrosia. The counterparts in Ages were just kind of meh. As for
LA, well, I can't really say. I just enjoyed playing it so much as a kid that playing it now brings back warm fuzzies, it's hard to point out why anything is objectively good.
That being said, I've never actually beaten any of them. x_x