Argh, this is probably one of the harder decisions ever.
1. Baldur's Gate 2/Throne of Bhaal (no reflection required, it's my favourite game of all time)
2. Planescape: Torment (I haven't even finished it, but goddamn is it ever good)
3. Final Fantasy VI (3D is for pansies)
4. Golden Sun/Golden Sun: Lost Age (need to dust off the ol' GBA and play through those again)
5. Mass Effect 2 (I liked it better than some of the games on this list, but calling it a full-blown RPG is stretching it)
Honorable mentions go to the Pokemon series, (Gold/Silver/HeartGold/Soulsilver), Kotor, Jade Empire, Final Fantasy 7, and finally Dragon Age coming in at a resounding "decent." Seriously, you call something the "spiritual successor to Baldur's Gate" and I expect a HELL of a lot better than that.