If you liked Monsters, Inc., you'll probably like Monsters University. If you didn't see or care for the first movie, there's not much reason to see the second. It's a competent followup, though a prequel rather than a sequel within continuity. The usual Pixar charm applies, though perhaps not so much as in some of their other franchises. Likewise the usual Pixar production values apply, which is always fun if you, like me, enjoy that sort of thing. Since I didn't see it in the theater I bought the Blu-Ray to go with my Monsters, Inc. DVD. I'm not sorry I did, but I would describe this as satisfying and entertaining without the depth of some of the stronger movies in the Pixar oeuvre. On the plus side, it doesn't suffer from whatever horrible rot afflicted Cars 2, either.
If you liked Thor in his other recent Marvel film incarnations, you'll probably like Thor: The Dark World. Witty banter, bombastic music, existential threats to the nine worlds, Natalie Portman, lots of punching and exploding. What's not to like, if that's your sort of thing? It's certainly mine, or can be. The best thing in the film was the twenty seconds or so where Loki turns into Captain America while haranguing his brother about his life choices. The fact that's the best thing in the film probably tells you everything else you need to know. (Caveat: if male physiques draw your eye and libido, that might be the second best thing in the film after the brief scene of Chris Hemsworth wiping the sweat of valor from his chiseled form.)
In other words, both movies nicely met my expectations as sequelae to their respective franchises, without surprising me or delighting me in any unanticipated ways. Which from contemporary Hollywood is something of a win.