Ok, so if your into story and willing to deal with less about gameplay and more about content, then i suggest you pick up a Bioware game such as mass effect series, or dragon age origins. From what people tell me, they think that the shooting in mass effect series is broken, i personally don't think so,but then again it's not me who's playing it. there is also dragon age, one of my favorite RPG's because of how much depth they put into the story. Even Dragon Age 2 was good.... course short and felt more of an expansion but still playable under $20 or 10 to 15 Euros.
But i see that your into action RPG's so most likely you would go for fable series, preferably one and two. (those are my favorite because you can customize your char. the most)
now i don't know between these two games, but Skyrim and oblivion are very good RPG's. The difference between these two games though is
Graphics
Story
Mood
Theme
and some Mechanics....oh yeah and dragons.
i prefer Oblivion because of the mood. everyone is happier in oblivion where as Skyrim everyone is all moopy or complete jerks, and racist.
There's also Fallout series, but it's basically the same thing as Oblivion/Skyrim with guns.
and last but not least, my favorite and you may actually love it also.
Bastion: my all time favorite game for its art style, gameplay and story. seeing as how you like Diablo 3, this may be the best game for you because it plays just like it with a style that looks like it was painted on a canvas. The music is a mixture of Western, and Eastern Cultures so the music goes amazingly with the game and just the different customization of weapons. i suggest you get or just look at this game.