If people have that impression of you, the only thing you can do and the one thing you need to do is prove them wrong. Show that you're different. Like someone already said, stand out from the crowd so people acknowledge you as that guy who's worth it.
Of course, you're going to get girls who are the type that complain about guys being dicks, but then turn around and solely go after dicks. These people are worth your time. Neither are people that are willing to generalize you.
There are a lot of people out there who suck, but there are some that don't and the process of finding someone that you want to spend the rest of your life with is the process of weeding through the shitty to find the good. But you have to really present yourself as admirable, commendable, and someone who will be different than the rest in a good way.