This is one of those cases of a movie that should have worked way better than it did.
Just the very idea of watching Earp and Mix solving some murder mystery in Holywood sounds incredible and fun to watch. However, Edwards' screenplay never truly finds its identity, floating between Neo-Noir, Western and Comedy. Maybe paired in Noir-Western or Comedy-Western it would've worked better: it just didn't know wheter to take itself seriously or not. That is, however, the only real problem with it.
The production and time setting is awesome, with a shoutout to the costume design. Mix's especially.
The colors are a sight to see, creating a warm-hot feel to the movie, reminiscent of the Western, but in a Noir setting.
Mancini's soundtrack is one of the best I've ever heard. Perhaps as a consequence of the film's lack of true identity, Mancini went every which way with it. His "Sunday west" bits combined with more somber and serious tracks - reminiscent of his work on Touch of Evil (1958) - just complete each other so well.
Willis is in a point in his career that is intersting to watch. Even before his greatest hit (and masterwork) Die Hard (1988), in which he hadn't found his persona yet. Still, he looks and sounds much like the star he would become months later, with a touch of Mix-cowboy in. He is a very "light" presence on-screen, and in the good way.
McDowell is always a convincing actor, and his "Happy Hobo" Alfie Alperin is quite fun to watch - especially given the parallels to another Happy Hobo, Chaplin's The Tramp - but he isn't given a lot of screen time, and from the very beginning, it's quite clear that he is the villain.
But the highlight of the film is the veteran James Garner. His incarnation of the legendary frontier lawman Wyatt Earp is (albeit anachronistic) one of the best. In my opinion, only second to Kurt Russell's in Tombstone (1993). That "hawk-eyed" archetype that Earp basically defines in pop-culture was very well-captured by Garner - even out of his "natural habitat" of the west.
Sunset is a very fun, lighthearted buddy movie. It is a great movie that should have been an all time classic, yet it somehow feels right. It's a one-of-a-kind curio piece. And my heart says it deseves more recognition. Give or take a star or two.