There are also a few interesting appearances from actors "before they were famous." Most notably, we see Patrick Stewart (Captain Picard of Star Trek, The Next Generation), and Liam Neeson, both in supporting roles.
I'd say this is my second favorite movie based on the Arthur legend. First prize has to go to the more recent King Arthur,with Clive Owen in the lead role (though that is a totally different story, so it's a lot like comparing a Model-T to a 1965 Mustang). That one gets top marks for story, acting, and special effects. I feel Excalibur's age has diminished its effectiveness, and thus it can't stand up to modern masterpieces.
Overall, I'll give Excalibur 3 stars. It's worth watching, but nothing really special.