Diablo 3 is a hack and slash with little to no storylines, no open world, no real exciting quests, it is pretty much as action as you can get in an action RPG. The main point of the game is grouping up with other people for loot over and over. Skyrim is obviously a single player game. While Diablo 3 can be played single player, like most Blizzard games, the main reason people play hundreds of hours is the multiplayer. Team aspect is great. Skyrim can't have that. Skyrim does have a lot of customability, large amount of ( albeit repititious ) quests, an actual storyline. They do play rather different. Diablo 3 IMO is better, but I didn't like Oblivion and never bothered with Skyrim TBQH. If you want a multiplayer game, Diablo 3. If you want that more "classic" RPG feel, Skyrim.