I think the key is variety, mixed with quality. The most unenthusiastic I have been for superhero films is The Amazing Spider-Man ones and I don't think they are bad at all in themselves, especially the first one. They just do the same thing again we'd seen barely a few years before. It's boring more than terrible.
The Wolverine concept is one we've seen several times, in the X-Men and 2 previous solo films. This one is not only better than the previous two but different. A such we've seen in the box office the issue isn't with the character or superhero concept or actors, it has made a shitload more with a smaller potential audience.