I had no problem with Brandon Routh as Superman. Reeve's performance was superior, especially in his embodiment of the more heroic side of Supes. Routh might be able to affect that as well, but the script for
Superman Returns was just more sombre than the Reeve flicks.
The only "stand up and cheer" scene was the jetliner rescue (though that was one awesome scene), so there wasn't much for Routh to grin about. By comparison, remember Reeve's introduction to Metropolis as Superman? He catches Lois and says, with a grin (like he's having fun), "Don't worry, miss, I've got you!" There were no moments like that in the
Returns script for us to see whether Routh could pull off that side of Superman - sheer joy in being a hero.
No, what bothered me about Routh was how the new suit looked on him. The guy was in very good shape, just as good as Reeve, but the suit as it was designed made him look lanky rather than powerful and commanding. Now here's the same suit design on a videogame version of Routh:
http://www.vgcore.com/media/1_1002/7.jpg
Notice that on a Superman whose physique is like the one we see in the comics, the
Returns suit actually works! But Routh doesn't have a physique like that (and neither did Reeve), so the suit has to be designed differently in order to achieve the
same powerful effect in a live-action version.