Why exactly are you 2 having conversations about women whom in his opinion are better looking than you?

I'm lost... I can't imagine (from what you've stated) that he randomly goes; "that girl's so much hotter than you babe"... so I'm having trouble mentally picturing the scenario you're attempting to paint here.

If its your opinion that they're more attractive and he's refusing to agree with your sentiment (and therefore being dishonest in your eyes) well then firstly, its still only your personal opinion, unless you can mind read.

Secondly, even if he does agree with you but refuses to admit it, that's smart, as you're insecure enough as it is and he probably doesn't want to make you feel worse about a woman that has zero effect on your relationship.

Sorry if I'm still not getting an accurate grasp of the situation, or if I'm way off base, but that's all I've got from what you've shared here.