I'm not entirely convinced the success of Deadpool is because it's simply rated R. I think there is fatigue but when it comes to heroes. All of the hero stories have become generic. Even this idea is already of the team fighting itself is being copied with Batman V Superman and we kinda saw it with Watchmen. Hell, theres some of it in the first Avengers. I think the success is largely because Deadpool is more of a gray area villain. I wouldn't be surprised if Suicide Squad outperforms Batman V Superman.