If you like lots of mouse clicking, crawling through a crap ton of dungeons and find a bunch of loot (and I mean a BUNCH), Diabo will be your choice. I heard the multiplayer can be really fun if you play with friends (especially the perma-death mode).
If you like an single player adventure, with some epic dragons fights well not as epic as Dragon's dogma with a expansive map with tons of locations to explore and an environment you can interact with. Then go with Skyrim. If you are getting the PC version, be happy since there are a ton of mods you can fool around with (like the tower defense mod :D and even a multilayer mod, at least last time I checked)
I would recommend another game called Dragon's Dogma though. It makes all the dragon fights in Skryim look pitiful. In Dogma, you can actually climb on top monsters anything from Griffins and Cyclops to Dragons (think Shadow of the Colossus) and crawl and attack on them on their backs or legs. Also to note, when it is night in the world of Dogma, it is freakin' night time. Unlike most games where night is just a change of scenery, Dogma's night will bring about dangerous creatures from ghost to skeletons and even zombies (also to note the wolves act like real wolves) that can really make you feel vulnerable and weak.
Though it's all up to you which game to get.