Well there have been a couple of "knights movies" in the 50's (like
Ivanhoe and
The Dark Avenger ), but those were hardly realistic.
Otherwise, I don't seem to recall any. El Cid, but that is not European knights vs. European knights.
Which reminds me, there would be a couple of great historic medieval battles that could be made into movies: Hastings, Stirling, Falkirk, Bannockburn, Crécy, to name just a few.
Are you reading this, Sir Ridley?