Planescape: Torment. So what else is good?
Fallout was already mentioned, and there's really not much I can say about it that isn't mindless gushing. Fallout 1 is what every cRPG should try to be. Period. It's the pinnacle.
KotOR 2, sadly, had the greatest potential to be a thousand times better then KotOR 1 - and for a good portion, is. Unfortunately, Lucas Arts wears it's pants on it's head, and decided to butcher the development time they originally set so they could release the game for Christmas, and much of the brilliance was lost. I actually suggest you read through the KotoR 2 Let's Play - they touch a lot on how amazing the game is, and what was lost when Lucas Arts decided to kill it.
Why wasn't Mask of the Betrayer mentioned? Sure, the Neverwinter Nights 2 original campaign was mostly eh (Better then NWN1's OC, mind you), but the expansion, Mask of the Betrayer, is absolutely amazing. Gann is probably my favorite partner/friend/companion from any non-PS:T game of all time, easily. The game is non-linear and has, bar none, the best "evil" path in any game ever made. For me, that game set the standard for how to make a non-linear game with evil choices.
Personally, I advise you stay away from Bioware. They've made an occupation from releasing the exact same game in different settings (Dragon Age is going to be Mass Effect in Middle Earth. Mass Effect was KotOR with some words changed. KotOR was Jade Empire in space. Jade Empire was NWN1 in bamboo covered Europe, not to be confused with Asia), so quite frankly, if you've played one, you very much have played them all. And god help you if you like realistic partners/friends/companions, because all Bioware seems to be capable of are whiny child-men who see the main character not as a sentient being, but as a walking psychologist. I'm positive that Bioware has personally set back the women's rights movement hundreds of years with their refusal to portray female PCs as anything but pathetic, mewling spellcasters. And why? It allows Bioware to give you the opportunity to discover these "strong women" who studied all their life to master the dark art but after removing a few layers you will discover that under this strong facade they are ony little scared girls who need love to survive in this harsh world. It makes me want to vomit.
Morrowind is a fun hiking simulator. I mean, don't get me wrong - the aesthetics, showing the in-game setting as somewhere that's wonderfully alien and fantastic, makes it one of the very, very few 3-D games that I enjoy since we decided not to go anywhere but medieval Europe, the in game lore regarding just about everything is awesome, and I absolutely adore pre-Oblivion Tamriel, one of the few settings with elves that are absolutely cool in just about every way - and Morrowind helped make the Dunmer one of my favorite races of anything from any setting, period. It's just...it's just...it's just that the gameplay and storytelling is kinda eehhhh.
Something similar goes for Arcanum, really. The setting is awesome. The in game lore is awesome. The storytelling for the most part is awesome. The gameplay? Not so awesome. The NPCs really need some work, too.
Keep in mind, despite my detractions, I still recommend all of the above games that aren't from Bioware. Morrowind? Play it! Mod it heavily, but play it! Arcanum? Grab Drog Black Tooth's mod for it, and through yourself in! Even KotoR 2 is a fun romp through a game that tries to make Star Wars one thousand times better as a setting.
On the jRPG - and thus, console - side, I agree fully with the nomination of Suikoden. 1 is great, 2 is absolutely fantastic - or awesome, if you want - and 3 is good. Four is...don't play four. It's not bad, it just doesn't match up with the greatness of the other Suikodens. Five jumps back up to great.
I dislike FF7. Sorry. 8 is worse. I did enjoy nine though! Ten...that's FF8 level. Sorry again.
Buuuuuuut...Final Fantasy Tactics is great stuff. It's got my recommendation.
I'm not much of a console gamer, so there's not much else I can through out, but I know a lot of people who absolutely adore the Persona series, and they all seem to agree that 4 is fantastic.
I like 4 (the problem of mortals wrestling with the choice between easy Evil and difficult Good), 6 (the massive cast and the epic plot threads), and 10 (the Journey and the Sacrifice!) for some of the best plots around, though 7 is certainly a strong contender (a certain famous death scene...). 
