You're running into what is the difficult part of being a woman, which is trying to tie down a potentially high-value man without being cast aside as another stepping stone in his life. There's really no "great" advice here since it probably depends solely on the desires of your boyfriend, and if he's unsure of what his wants are, then he's going to say things that later don't match his actions.
It could very well be true that he wants to settle down. One thing you need to remember is that, assuming this guy dated some extremely physically attractive women, he may have encountered some soulfully "empty" ones as well. It's very possible these women caused a ton of drama in his life, and maybe his tastes have changed. Every time he sees a "G-cup" girl walking down the street, maybe it reminds him of all the terrible situations he was in with his ex. Or maybe he misses it -- it's difficult to tell, and that's why it's difficult being a woman. We encourage guys on here to be honest with their intentions with women, but we do that because we know the majority of men out there are either (a) not honest or (b) think they want one thing and then flip-flop and want something else.
As to your question about whether or not men compare partners, let me ask you this: do you ever compare him to your previous boyfriends/lovers? Or do you compare previous boyfriends/lovers to the ones before them? Most likely the answer to this is "yes." It is my belief that everyone compares, especially if one is looking to enter a long-term relationship with a person. It's just a natural thing to do when spending lots of intimate time with another individual -- you're likely to compare those times with other ones that you've had in the past.
As a woman, you need to find the balance between showing love and appreciation for your man without smothering him with attention. Find out about what things he really loves, and attempt to help him achieve those things. Simultaneously, give him space when he desires it. And of course, as much as it may pain you to hear it, always be prepared to exit the relationship if you believe it's no longer healthy for you to be in it. What is "healthy" should be determined by you and your feelings, so if your feelings are mostly negative, then perhaps the relationship is not meant to be. On the other hand, if you are very content with the way things are going, then there's no reason to change what isn't broken.