world-class vs best

world-class is not a noun while best is a noun.

Word	Noun	Adjective	Verb	Adverb
world-class	No	Yes	No	No
best	Yes	Yes	Yes	Yes

world-class (noun)	best (noun)
	the supreme effort one can make
	the person who is most outstanding or excellent; someone who tops all others

world-class (adjective)	best (adjective)
ranking above all others	(superlative of `good') having the most positive qualities
	(comparative and superlative of `well') wiser or more advantageous and hence advisable

world-class (verb)	best (verb)
	get the better of

world-class (adverb)	best (adverb)
	it would be sensible
	in a most excellent way or manner
	from a position of superiority or authority