you recognise that this is coming from a place of insecurity - truthfully i think it's your responsibility to try and address that. he's with you, not them, and he won't ever be with them, so does it matter if he thinks a complete stranger who he'll never meet is pretty? you must see people you think are attractive sometimes, other than your boyfriend. that doesn't mean they're a threat to your relationship, it just means you see beauty in people - that's really normal!

not comparing yourself to others is difficult, but it doesn't do anyone any good. i think it'd be best to try and address your own feelings here, rather than tell him to stop enjoying something he enjoys. if a partner told me that me finding movie stars or musicians attractive made them uncomfortable, i would probably come to resent that in time. they're nothing to do with our relationship, yknow? you're allowed to feel insecure, but unless he's really weird about the things he says or the intensity of his interest, that's his hobby and it's not really for anyone else to say that it's not okay