Certainly there are some books or movies that are hard to classify, but there's generally a primary theme-- a Western is a Western, whether it's comedy or drama, realistic or fanciful.
If a Western is a Western, regardless of other genres, does that mean Outland
, Four Brothers
, and Star Wars
are all principally Westerns? All have been evaluated by genre critics in terms of the Western, and the first two are both loose remakes of earlier, more traditional Westerns (High Noon
and The Sons of Katie Elder
And what about "Westerns" that pre-date the establishment of the Western film genre, like The Great Train Robbery
(1903), which was sold as a crime film and, when successful, led to a cycle of other crime films, not films that have been since grandfathered into the Western genre?