What is the best Marilyn Monroe movie?

River of No Return

A 1954 CinemaScope Western adventure directed by Otto Preminger, featuring Monroe as a saloon singer swept into a dangerous river escape with Robert Mitchum.

Niagara

A 1953 Technicolor film noir thriller set at Niagara Falls, where Monroe plays a scheming wife plotting her husband's murder — an early role that cemented her as a serious actress.