Be brave and try Planescape Torment. You'll be playing from an isometric view but you're in for a treat.
Depending on what you define an RPG as there're a lot of choices. For me it's not a case of stat sheets and inventory and more to do with characters, choices, dialogue and story. You'll likely have combat whatever you go for so here's a couple that you'll likely have heard of and some you might not that ought to be worth a look.
Risen - No choice of character, exploration, factions, heavy on the sword fighting.
Morrowind - Play it modded and it can be pretty much anything. I'm currently playing a pregnant craftswoman who spent a long time in the Imperial Cult, nevermind playing the main quest

. A varied and special game.
Mass Effect 2 - Sci-fi setting, choices, wonderfully written characters, brilliant rollercoaster ride through building a party and taking them on a climatic mission.
GTA IV - Fantastic characters and choices, you're playing a single character but can in some ways define them. For me this is playing a role and exploring a brilliantly crafted world. No stats and inventory made me doubly happy.
Dragon Age Origins - Medieval setting, party building, good dialogue though you are rather funnelled through the story.
Fallout 1 + 2 (isometric view) - Wry, clever, well written and lots of scope for crafting the character the way you want to.
Deus Ex - Smart and thoughtful, can be played peacefully or viciously, a real treat.
Vampire Bloodlines - A lesser known but lovingly made game with great writing and characters with a wide choice of character development options and factions.
Just a big warning, Mass Effect 2 was a big failure.
??? It was a massive success though you may not have enjoyed it. I felt Oblivion was a tedious waste of hard drive space, it was still a huge success though.