Non-MMO?? Hmmm, actually that might be a good idea. A lot of the fun in an MMO comes from the quality of the friends you make in the game, which makes it hard to distinguish a good game from a not-so-good game. (But City of Heroes is still the best, anyway.
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RPGs… Let's see…
Oblivion - It gets a lot of hate around here but I really loved this game. Especially with a few mods to make the natural environments look even better and that mod to add more hotkeys. The quests were great ("Oh my poor rats!"), exploration was fun, the landscape was gorgeous, and Shivering Island was a real blast. The 'butterfly room' was one of this decade's high points for sure.
Dragon Age I'm not even done with it but it's been very impressive. Good quests, good humor, excellent battles, strong character development - this is definitely one of my favorite games. And, unlike some other Bioware games not on this list, it doesn't get stupidly easy as time goes on.
Shadow Hearts: Covenant When I first started playing this, I didn't like it at all. I mean, the German commander in this World War 1 battle is a sexy young woman? Are you insane? But then it became clear that the answer was yes, they were quite insane. The irreverant characters were great (and sometimes rather disturbing), the story was OK, the humor was great, and the battles were quite fun, too, thanks to the "judgement ring." When you attacked, a marker would spin around a circle with some good sized green areas that count as hits and tiny areas that count as criticals. It worked quite well and made the turn based JRPG have a little action element.
Xenosaga Great combat and a great story. I really liked how the game plopped you right into a complex, high-tech universe and let you figure out all the buzz words for yourself. A lot of folks hated the huge cutscenes but I just put my controller down and enjoyed them. It's a pity the second game in the series had such an awful combat system. The second game's failure forced them to cut the series short and try to cram three games' worth of plot into the last game - ugh.
Baldur's Gate 2 - at least I think it was pretty good. It was friggin' 9.75 years ago, about all I can remember is Minsc! Oh, and walking into some town and having half a dozen people mob me to offer me quests. And, of course, gathering my party before venturing %#()$! forth.
Neverwinter Nights 2 + Mask of the Betrayer - I got to play my character all the way up into super high levels! And the stories were well done, too. I loved building up that castle.
I have to admit, there's serious role playing in X3: Terran Conflict. Quite a bit more role playing than you'll see in action RPGs, that's for sure. It's a flawed game but the flaws are easy to overlook given that titanic scale of the game. Definitely one of my favorites of the decade, though I'm not sure I would call it an RPG. (I would actually call it an Elite-like game.)