genius vs ace

genius and ace both are nouns.

Word	Noun	Adjective	Verb	Adverb
genius	Yes	No	No	No
ace	Yes	Yes	Yes	No

As nouns, genius and ace are synonyms defined as:

Other synonyms of genius include adept, champion, hotshot, maven, mavin, sensation, star, superstar, virtuoso, whiz, whizz, wiz, wizard.

genius (noun)	ace (noun)
exceptional creative ability	a serve that the receiver is unable to reach
a natural talent	one of four playing cards in a deck having a single pip on its face
unusual mental ability	someone who is dazzlingly skilled in any field
someone who has exceptional intellectual ability and originality	the smallest whole number or a numeral representing this number
someone who is dazzlingly skilled in any field

genius (adjective)	ace (adjective)
	of the highest quality