Not sure if I should post this here, or in the general forum, but here goes...

Finished this game just last week (it was the reason I signed up with gog.com, and one of those old games I really wanted to try), and I loved it... great story, great characters, overall great experience.

However, now I'm at a loss as to what to go for next... I've been playing Icewind Dale (played it years ago, liked it), but even with the NPC mod, the story is just not enough for me, and I'm not really enjoying the gameplay at this point. Years ago, I played and beat Baldur's Gate 1 and 2 (good games), so I'm not really looking to get back into those. But I would really like to pick up another good old game (preferably an rpg) with some story and good characters to it. Suggestions?

Games I've already played:
Planescape (duh)
Baldur's Gate 1 and 2, both expansions
Icewind Dale 1, both expansions (I've played IWD2 just a bit)
Fallout 1 (only played 2 for a few minutes)

I haven't played Arcanum (any good?), or the just released Temple of Elemental Evil (any story, or is it just a dungeon crawl?).

Fallout and Arcanum games are the only ones that really come in mind. There are no other games similar to Planescape. Actually, there are NO games REALLY similar to Planescape. I WOULD recommend buying Fallout 1, it is hard to get into, but VERY good, both story and gameplay-wise.

There's never been another game like PST and sadly I doubt there ever will be. Vampire The Masquerade: Redemption might be worth considering, it has a distinct action RPG feel but that's balanced by the story and characters

Planescape: Torment is unique, the only games who have a similar plot are (surprise) two "modern" Obsidian games (the first Neverwinter Nights 2 expansion and Knights of the Old Republic 2), but they are nowhere as good as PS:T.

Temple of Elemental Evil is mainly a dungeon crawl, think about a turn-based Icewind Dale.

If GOG will release Icewind Dale 2, you might want to try it. It has a better plot than IWD1, better conversations and if you install its NPC mod, it becomes even more enjoyable - however, not as good as Planescape.

Arcanum is kinda like a fantasy/steampunk Fallout. The characters are more fleshed out and the story and setting were more interesting for me than those of Fallout, but they're comparable. It's a great game really, but nothing like Torment.

Like Epantiras said, closest thing to Torment that I've played is Mask of the Betrayer, the first NWN2 expansion. Kotor2 also has a somewhat similar vibe to it.

Another game in which I've enjoyed the dialogs is Vampire the Masquerade : Bloodlines. There isn't as much of it as in Torment, and they're not as deep, but they're well written and enjoyable, espcially when playing a Malkavian character. There are a few great characters and while the story doesn't feel particularly epic, the ending is pretty good (well, at least one of the endings is. There's a pretty crappy ending too, but if you end up getting that one, you deserve it)

If you're willing to consider other genres, some adventure games have interesting stories and atmosphere to them (I really liked The Longest Journey, even though the best parts were at the beginning). Beyond Good and Evil was another memorable experience. Nothing like Torment of course but BGE's story, characters and overall style really hooked me.