I like Black Panther and feel that it's very well done, but I've seen it only once, so I'll have to see it at least once more before I can figure out where I'd rank it among the MCU movies.
At the moment, I think there are several MCU movies I like even more, including Thor: Ragnarok, both Captain America movies, Guardians of the Galaxy Vol. 1, and both Avengers movies.
As for the DC movies, I like Wonder Woman the best so far—in fact, I feel it's the only DC movie so far that's been done well. Justice League was okay, a little disappointing.
I'm really looking forward to Infinity War, even though I'm sure at least one hero is going to die, and that's really gonna bum me out, especially if it's Cap or Iron Man.