Nice usually means. Oh that is ok, it's pretty good. Pretty usually means. Oh that is extra nice usually towards something more feminine. What a pretty baby girl. What a pretty picture. Beautiful usually means. Wow! That is much better than nice. Wow, such a beautiful (idea, person, song, picture, place). I am surprised at how very very nice that is!

Pretty means something that has the quality of beauty (a song, a person, etc.) and beautiful is the same, but more so. "Beautiful" would be the next step from "pretty". "What a pretty kitty!" "Such a beautiful cat!" Or it could be a pretty song, a beautiful poem, pretty hair...anything aesthetically pleasing to the ears or eyes. Nice means good, agreeable, and implies friendliness, more of an abstract quality than pretty or beautiful. "He is a nice person." "That is a nice dog." "I had a nice walk in the park." I hope this helps!