My dog doesn't get along with others?

My dog is about five years old and he doesn't get along well with other dogs, we got him when he was about a year and a half and we have two other dogs that he gets along really well with. Is it too late to train him to be good around other dogs? We go to the park every day and sometimes there are other dogs there, he totally freaks out and whines and barks and pulls. If he gets near them he will try to snap, sometimes he'll get away from me because he is a very strong dog and he'll run up to them but he won't snap unless he is on the leash. I tell him NO in a strict voice but he doesn't listen when there are other dogs involved. I don't know if any of this makes sense, but I need help. It sucks that he can't get along well with other dogs because my two other dogs love to be social.