What's it mean if a girl tells a guy he's amazing?

That is a very good thing! I tell my boyfriend he's amazing. :) I tell him that because I think he's really sweet, smart, caring, and cute and because he is very important to me. The girl who told you that possibly likes you a lot. ^_^

Of course it's good. I tell this boy he's amazing all of the time cause I like him a lot. She either see's you as an amazing friend or she might be into you (:

If a girl told me I was amazing, I would have said I know I am, or yup I know its almost like a curse on how amazing I am. What were you doing that made her say your amazing? Did you do something nice for her, if that's the case it just be like her saying oh thank you so much your a life saver or something like that. So if that's the case she could just be being friendly. It really depends on the context and what you did for her to say your amazing. So what did you do for her to say that?

Depends on the context, if your talking about yourself loads it may be sarcasm, if your being humble or casually mentioned something she impressed, if you just met her she really likes.