definitely a form of insult. its one of those words you cant really see as a compliment, if used as is "pretty boy." you can say, "man this guy over here (point to friend) he's too pretty for his own good! getting all our gfs to buy him cake for his birthday, how did you do that man." its playful. now try it like this:
"man this pretty boy over here (point to friend) he's too pretty for his own good! getting all our gfs to buy him cake for his birthday, how did you do that man."
its def used to insinuate that you are a bit girly or a bit of a pansy. so yes you should not take it as a compliment when you hear it, but you dont have to get offended by it either. most guys say that bc they feel the other guy really could take his girl bc he possess a look the first guy believes might be attractive to women, even if its not so. they are insecure and say it as a pre-emptive strike kinna deal.
so many guys wanna pin me as the pretty boy just bc of the long hair. my face isnt good looking, but i have long hair. most guys just see the hair and think ladies would like that. so they get defensive and always pull their gfs closer and stare at me ha ha. i think long hair is more tarzan/conan carbarian/wild man. the world would be too simple if long hair guys did it to look good.
but back on topic, you can call a guy pretty as a joke between friends. but for some reason "pretty-boy" is for ppl who dont exactly wnat to be cool with each other. its like you can call your friend a tough (space) guy. but when you say "oh look at tough-guy over here." or "oh yeah, john's such a tough-guy" it insinuates that they "try" too hard to be tough.