Depends!!
It all depends on the person's class and the person that you are trying to tell it to.
This is just my opinion:
If the person is a tiguere and has no class, he may say something like: "oye mami, tengo ganas de rapar(sorry to be so blunt)". And lets not forget the lowlive''s favorite: "sing**.
If the person is classy and really know how to treat a lady, he may say something like: " me gustaria hacerte el amor" or "tengo deseos de estar contigo".
When I was younger, I used the corniest line ever, I would say "mi amor, tu cuerpo es mi templo y quisiera descubir cada pulgada de el". How pathetic, although it worked all the time, hehe!. I guess that they were VERY desperate, hehe!!.