topnotch vs ace

topnotch is not a noun while ace is a noun.

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

As adjectives, topnotch and ace are synonyms defined as:

Other synonyms of topnotch include A-one, crack, first-rate, super, tiptop, top-notch, tops.

topnotch (noun)	ace (noun)
	a serve that the receiver is unable to reach
	one of four playing cards in a deck having a single pip on its face
	someone who is dazzlingly skilled in any field
	the smallest whole number or a numeral representing this number

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