Well, obviously this is a matter of opinion, since I for one don't think Xenogears is better. Fighting in the gears got boring quickly and the exposition near the end since apparently they ran out of time/money/disc space turned me off.

I think the only other RPG that comes close to FF is Chrono Trigger. That game is just magnificent. It really has no faults at all. Great story, great characters, fun battles, plenty of extras. Chrono Cross is good too but it doesn't hold a candle to FF.

Same with the DQ series. Only DQVIII for me comes close to rivaling the FF games, probably because it is the most similar to FF than any of the other games (which turned off a lot of DQ fans I've noticed).

KH is a great series of games but it doesn't really compare well to FF since the gameplay is a lot different. Same with Secret of Mana, another great Square game. I love those series but they still don't beat FF.