我爱(愛)你 ngo5 ngoi3 nei5 = I love you.
How do you say "you love me"?
Just reverse the words: 你爱我nei5 ngoi3 ngo5 (Isn't Cantonese simpler than English? You bet!)
Note: Young native speakers nowadays tend to use "lei5 (懶音 lazy sound)" for "你nei5 (you)". For beginners, we'd better use "n" instead of "l". Meanwhile, understanding that many people use "lazy sounds" is helpful.
You may refer to http://en.wikipedia.org/wiki/Proper_Cantonese_pronunciation
for more info about 懶音 lazy sound.