Himself refers to God. It's a compliment. It says God did more than his best when He created you.

out do himself/herself/yourself/myself/themselves means to make more than the usual effort. It means to work extra hard on something. It's used to compliment somebody. "Wow you really outdid yourself on that presentation!"

Outdid is the past tense of outdo. To do more or better than in performance or action. to surpass or exceed in performance or execution