Lol, my brothers just found out about this, and they're confused as hell. I personally don't care, but if the end of the world is near as "prophesied" by I Am Legend judging from the Batman and Superman logo that was in New York, then I'll be a bit more concerned about something else other than a movie I'm never going to see.
And I don't remember Ben Affleck that much, honestly. I've seen Pearl Harbor and Armageddon, but I didn't know who he played in those movies, nor did I care. The only thing that pops into mind hearing "Affleck" is "Aflac". And even then, even if he's a bad actor and possibly got better overtime, how do we know that the movie will be good anyway? We don't know what's in the script yet. And considering how I've only heard really good or really bad things about Man of Steel, I think it'll be the same thing here. I doubt this movie will kill superhero movies (though didn't Green Lantern almost kill superhero movies much like Superman IV nearly killed Superman?), but if it kills crossover superhero movies that's not the Avengers, then all fingers can be pointed at something about this movie.
For now, let's just wait and see what happens. If you don't like Ben Affleck, no one's stopping you from not seeing the movie. But if you want to see the movie, don't let it bother you and remind yourself that the other half of the money will go to whomever's Superman.