Whether or not you will enjoy Napoleon depends on whether you are looking to watch a comedy or a historical epic.
As a comedy I give it a solid 4 stars. Watching Joaquin Phoenix walking around for the better part of three hours looking thoroughly confused about what he was supposed to be portraying or conveying was very amusing, especially combined with his mascot, The Hat, which he rarely removed.
Then there is the fact that his age doesn't change once over the course of his career from the age of 24 to his death at 51, which adds to the general air of absurdity hanging over the film.
So from this perspective it is endearing.
As a historical epic it falls flat on its face because there is simply too much material to cover in a single film.
A historical epic could have been made out of his invasion of Russia alone, or out of Waterloo and Austerlitz. Instead we gloss over this major historical and military milestones in minutes.
The whole film is stretched so thin that it has no historical or emotional depth.
The romance between Napoleon and Josephine is the only persistent story arc in the film, but should also have been a film in its own right. Instead of drawing me in emotionally it just added more content for the director to cover, further compacting the time used to cover other events in Napoleon's life.
All that said, it gets 2 stars because I was amused enough to watch it to the end. The portrayal of Waterloo also gets slightly more attention than other scenes and is at least entertaining to watch, although apparently historically inaccurate.