I understand your cynicism. I was just like you. But trust me, it's not necessary that you have to have other motives, you can really be genuine and sincere about your compliment. I do not actively work on trying to compliment people. The only thing I have changed is that if I have something nice to say to someone, I don't held it back anymore.
I think the core point that divides creepy/suspicious compliments and genuine ones is your motivation behind them. If you're searching desperately for something nice to say to the girl at the crosswalk because she has great cleavage, it's never going to sound sincere, and she will pick up on it.
However, the exact same compliment delivered out of a motivation simply to put a smile on someone's face can go a lot further. I used to wear quite quirky clothing and getting a compliment on my wardrobe choice would make my day. When I give someone a compliment, that's what I'm trying to achieve - I'm not trying to make myself feel good, or get in their pants, I just want to pass on some of the good will and good feeling that has come my way in life.
