best vs world-class

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

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

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

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

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

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