Easily Black Panther.
While I enjoyed Dr Strange, it was essentially Iron Man - with magic. It was fun, but felt too formulaic, whereas BP hit a ton of familar plot points, but managed to do it in a way that felt fresh.
Both Cumberbatch and Boseman were solid leads. It's tough to pick the better supporting cast - I'm going to give the slight edge to BP, because everyone, and I mean everyone from Bassett to Serkis, were terrific. Swinton was amazing in Dr S. but I felt that Mads Mikkelsen and Chiwetel Ejiofor felt very one-note (especially Mads).
Ant-Man, yeah not bad but not as engaging as either of the other choices in this poll.
As far as solo movies go I would say that BP is nearly on a par with Iron Man,
although not as good as CW. However, Marvel's group movies ( GOTG, CW, Avengers are still a cut above).
BTW - Why isn't Homecoming in this poll ? Iron Man cameos in it, but otherwise its a Spidey-flick.
Cheers.