Well, Kuato, no superhero movie has had perfect casting. The vast majority of people going to see these movies have no strong opinions about casting choices, so whatever we might think of who should be playing what parts has little or no bearing on the movies' success or failure.
I think that if you can acknowledge the fact that Superman is vastly popular and widely recognized, as well as being lighter and more kid-friendly than something like Batman Begins, then you can also understand the huge potential that Singer's film has. My prediction is that Superman Returns will succeed in selling itself as a special event, and droves of people who otherwise would not be interested will want to participate.
Most of the people going to see this movie will be seeing Superman on the big screen for the first time. Others will be just as eager to see a new Superman movie as they were to see Batman Begins, even though the timespan between BB and B&R was much shorter than the span between SR and Superman IV, and despite the fact that B&R was hated much more widely and deeply than Superman IV. So, the previous movies and TV series will be far from a hindrance. Rather, people who've seen Superman before, and enjoyed what they saw, will be among the most dedicated audiences, assuming all goes well.
But even more than that, I personally believe there are lots of people who feel just the same way you do about Superman in general, but it won't keep them from going to see this movie when it comes out...