What you say and how you say it is often the difference between a compliment and a catcall. It is often the difference between all the ladies looking forward to seeing you in the morning or walking away as soon as they see you.
At the end, it is up to you to be either a complimenter or a creep.
A vital lesson that has stuck with me over the years is that the distance from admiration to jealousy is shorter than the distance from my thumb to my pinkie finger.
In my opinion, they are two sides of the same coin.