I liked the Last Samurai, even if it did portray the Samurai as noble defenders of the people instead of the elitist bullies that they were in real life.
Troy was also entertaining. Not a classic, but not bad either.
Kingdom of Heaven was only so-so. The battle scenes at the end were awesome, but I was annoyed by the movie's obvious pro-Islam, anti-Christian bias. Not to mention that I can't stand Orlando Bloom.
King Arthur was bad. I'm far from being a movie snob, but even I had trouble finding things to like about this one.
I haven't seen Alexander, but from what I've heard from people who have seen it, I'm only missing a long, boring, bisexual angst-fest that's occasionally broken up by battle scenes. I've also read reports of the film breaking in theaters where Alexander was playing, and the audiance applauding.
Given the choices presented, I'd pick the Last Samurai as the best post-Gladiator epic.