I know this sounds dumb, but what do you call people who are rich but they act normal, don't try to show off at all, and is very kind.

Answer 1

Possibly the opposite (antonym) for "snob"?

http://www.powerthesaurus.org/snob/antonyms

Answer 2

Down the earth????
Basically the opposite of having pride

Answer 3

down to earth <~~yes, that works, too.