Honourable Mention: Batman
Yes, these two are about to share a movie of their own, but Batman and Superman being a constant presence in each other’s lives should continue to be a big part of their respective stories moving forward.
With the heroes set to put their differences aside to form the Justice League, a rematch is probably off the cards, but another team-up would certainly be possible, and using their respective solo outing to build up to that would be great for fans and makes perfect business sense for Warner Bros.
So, why not have Bruce Wayne show up at The Daily Planet or Superman arriving in Gotham City to ask for the Caped Crusader’s advice? After all, stuff like this is what a shared universe is meant for, and the Man of Steel sequel should definitely take advantage of that.