Thor: The Dark World is often considered one of the MCU's lowest points, and for understandable reasons. It's not necessarily visually appealing, most of the Asgardian supporting cast is wasted, it spends too much time on Earth rather than going cosmic, the chemistry between Natalie Portman and Hemsworth leaves something to be desired, and even the main character himself often has the movie stolen right out from under him by Tom Hiddleston's Loki, among other frequently discussed issues.
That said, if you can set aside the overwhelming feeling that the film fails to live up to the potential the first film queued up for it to capitalize on and look past its myriad of faults, it's still a relatively enjoyable watch, and gives Thor more to do overall than Age of Ultron, which is why Thor's own sequel edges out the Avengers follow-up on this list.
Even though Thor is frequently outshone by the much more magnetic Loki, Hemsworth still does a good job with what material he's given, particularly when the character gets to interact with others like Odin, Sif and the Warriors Three, and, of course, his own brother. What's more, the final, portal-hopping fight scene with Malekith is pretty slick. Overall, though, Thor didn't have his worldview memorably challenged and life upended in the way that, say, The Winter Soldier did to Captain America the following year, which left The Dark World feeling more like a harmless little adventure rather than the gamechanger for the character it could've (and should've) been as a result.