Superhero movies have essentially become a genre unto themselves in recent years and Marvel Studios is a large reason for that. Marvel now makes up to three films in a year, and when you add in the other superhero movies that get made, we end up with quite a lot of them. However, Marvel Studios chief Kevin Feige isn't worried about people being burned out by superhero movies. Just because they're all superhero stories, doesn't mean they all have to be the same. As long as the films tell different sorts of stories with different sorts of characters, superhero movies should be fine. In his words...
That's the reason we make the movies we make and the way we make them. For years, predating the history of Marvel Studios itself, people asked me about superhero fatigue and if it was a fad or a phase. I say, if they're all different, if they're all special, nobody will get tired of these things before we at Marvel Studios will, since we live and breathe these things 24 hours a day. You make films like Thor: Ragnarok, like Homecoming, like Guardians of the Galaxy, certainly like Panther, and the upcoming Infinity War to keep it interesting and change it up. And we will continue to do that.
One of the reasons that comic book superheroes have remained so popular over the years is likely in part because of the wild diversity between them. Different sorts of characters lend themselves to different sorts of comics, and each comic book finds an audience, even if the overall comic book audience isn't interested in every book. The same thing is happening when those characters are brought to the big screen. You might be a fan of a certain character, but you could also just end up liking Ant-Man because you're a fan of heist movies or Captain America: The Winter Soldier because you like films with political intrigue.
But of course, there's the added benefit, for Marvel, that if you do get attached to a particular character or story, you might come back and watch the other films to see how it plays out. Like when you used to (or still do) buy a comic book you never read because a character you liked was making a guest appearance.
Not every movie is designed to appeal to every audience, and the fact is that remains true even among Marvel movies and superhero movies in general. Even for those of us that do see them all, the way they change things up keeps us from getting bored. It also, as Kevin Feige tells Vulture, keeps the people at Marvel from getting bored.