I second Golden Sun as a non-Final Fantasy RPG.
Having said that, Final Fantasy Tactics is a ton of fun (in 30-45 minute bursts, imo) and Final Fantasy IV (II on the SNES) is an insane amount of fun.
I really wanted to like Car Battler Joe because it's the only other game I know that mixes RPGs with racing, but it's nowhere near as fun as Final Lap Twin.
You can find a Phantasy Star Collection for the GBA which includes I, II, and III. I think it's worth it for the first one.
Sigma Star Saga is an RPG where you have mini shmup levels instead of traditional turn-based battles. It's a cool concept but you may be tired of it before a long flight is over. I still like playing it in spurts, but I don't anticipate finishing it.
I enjoyed Lunar Legend, but I've never played any of the other Lunar games.