He compared me to his exes, why?

I've been seeing this guy for a few months and I really liked him until today. We like randomly sending each other faceless naughty pics sometimes. After sending him a pic of my boobs (no face), he said that I was in the top 3 for boobs and top 5 for hottest women he has ever been with. That comment immediately had me thinking wtf, turned me off, and gave me the ick. I feel like he could've just said,"Nice!" or , "Thanks!", or some silly emoji, not making it feel like I'm suddenly in some competition. Why would a guy do this?

He compared me to his exes, why?
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