If that "so much better" means that he could have dated other girls who are much much better than her current girlfriend, you'll just make your friendship with your friend worse because he's in the state of "so much in love" with that girl and usually people in love will refuse to acknowledge the negative sides of their partners even though it's the truth. I think you should just support him and be with him just like before he dated her. He'll realize whether she's good for him or not in time. In the mean time.. you just need to bear with your feelings and keep on supporting him. Good luck!
