I'm so torn between Dark Souls and Skyrim. Both are amazing game experiences, deep and rewarding. I adore the exploration and combat, and sense of dread and looming death in Dark Souls, most fights are to the death. Later on this gets a bit easier as your stats level up but early on every fight is epic, and it rewards you for learning and using combat. The downside of Dark Souls was the lore and the world doesn't really give you much to go on, it took me forever to figure some things out, and granted there is a great Dark Souls wiki but there really should be more of to the story, more of the lore available in game.
Skyrim is much slower paced but no less beautiful to explore, it's world just sucks you in, with its lore and it's amazing vistas. The combat isn't very good, it does the job I've tried a few different combat modes and the magic felt underpowered, and the melee was just clunky, the ranged bow combat felt pretty good, but overall I'd say the combat is Skyrim's weakest point, not to say this majorly detracts from the experience. The rest of the game though is a wonder, every dungeon filled with danger, vast distances to explore, puzzles to figure out, and a grand addictive story just waiting to be discovered.
If Skyrim and Dark Souls had a baby......holy s**t