I think it's less important what we think and much more important what you think and feel. I feel from reading your writing that you don't feel it is appropriate to be comparing you to his ex and that he is too close to his ex. This is something I advise you be careful about. It's not always a good idea to get into a relationship with someone when they have only just ended one. Often that person needs time and space to re-establish themselves as an individual person. And sometimes when people break up, it doesn't mean that it's over. Look at Pink for heaven's sake, she got divorced and then remarried to her ex. He is the father of her child and that means that they will need to interact. He needs to be properly invested in the relationship with you, to not end up being pulled back into his ex's life. It's difficult to be sure he is not with you as a safety net, why did you get together? How long have you been together now? Sometimes you need to look at the reasons for why you are asking questions and how you feel in order to work out what you want to do next.
All the best,