Oblivion is one of the greatest RPGs I've played, and should be tried whether or not you like this kind of gaming.
You play as some sort of hero, although you start inside a prison cell. The emperor tells you that you will be the hero of the land and you're going to close this hellish realm called Oblivion, which is spewing out demons all across of Tamriel. He tells you he's gonna die and he gives the Amulet of Kings, tells you to go see some guy. Now you're left outside the sewers faced with this huge world of fantasy. You can go do what the emperor told you to, or you can ignore it completely and go off joining these criminal groups such as the thieves guild or the dark brotherhood. Essentially, you are bound by no quest or mission, you can just wander around Tamriel being whoever you want to be. You can attack anything in this game. Take (or steal) almost every item you see. Of course by being a criminal your bounty rises and guards will become hostile. If you go to jail you lose skills and stuff.
Oblivion also has a great combat system. You fight in real time and it looks like a cool action game due to the nice graphics and animations. You press one button to swing your sword and it works. The physics are great and blood splurts about and gets on the walls. But there is a lot of good RPG magic going on behind this flashy spell casting and sword swinging. You get to choose from a long list of classes (or make your own) then level up stats like personality, stealth, destruction, etc...and the game handles all these thing very well. You're going to have a lot of fun with it, trust me.
It all ends of creating an awesome game that everyone has to try and some point or the other.