"Hamlet" is said to be the most interesting play ever written.
Literal
"Hamlet" [topic-は] up-to-now [of-で] most interesting drama [copula-だ] [quotative-と] say-passive [progressive-ている].
Two notable features. 言われている is the passive ~れる (言う → 言われる) in ~ている form — 'is said,' marking commonly-held opinion. これまで ('up to now') + で forms a superlative domain: 'among all that has come until now.' 戯曲 ('drama, play') is the literary word for a theatrical work.