I think probably Shadow Hearts 2: Covenant. I've played Final Fantasy XII and Lost Odyssey since, but got bored with both of them. I might go back to Lost Odyssey, since I'm on the final disc. I also recently got Shadow Hearts 3: From the New World. It's alright, but not a patch on Covenant.
Why did I like Covenant so much? Well, it didn't take itself too seriously, and made me laugh on many occasions. The game world was interesting and well thought out, and I liked the alternative history WWI idea for it. The fight mechanics were good, the judgement ring kept you interested when going through fight after fight. I would've loved to have seen what Shadow Hearts' developers could have done if they were given the same resources as Final Fantasy is; although I suppose since a lot of the developers ended up working on Lost Odyssey, I've partially got my answer.