This is what I get for coming to the thread late: all the good movies are already taken, and Maggot's wearing the same dress as me...
I would also add Hawk the Slayer. It's cheesey, but so are most LARP's, plus the acting, dialoge, and storyline are fairly similar to many live-action fantasy games.
Shichinin No Samurai, a.k.a. The Seven Samurai. It's medieval, if not European medieval, and just a really great piece of cinema.
While it's not a Dark Ages setting, The Adventures of Buckaroo Banzai Across the 8th Dimension is certainly fantasy, and is arguably the ultimate roleplaying movie.