Mediocre movie according to whom?
SR has a tomatometer of 76% among the critics and 67% for the audience,
on IMDB it has an average vote of 6.6 (Superman II has 6.7).
Some people should learn that their opinion is not always the same one of the whole universe.
Ghost Rider (5.2 on IMDB) is getting a sequel where the only thing left from the first one is the actor. They're not calling it a reboot, but they changed everything else, bike included.
From my first sentence where I said "I do think that Routh did make a pretty good Superman who unfortunately got lost in a mediocre movie." I would say that I'm saying it was a mediocre movie which is my opinion - thus the opening of the sentence with "I do think..."!
We can sight numbers out of the ying yang regarding if a movie was good or not but that's not the point here. The question is will Routh be back in the role. As I said I "thought" he was good and personaly would have no problems with him back in the suit - but I also think/know it's not going to happen and that Nolan and Snyder will be starting with everything fresh - including the lead part of their movie.