The unfortunate M.O. of Hollywood is to trump history in favor of "plot"- I use that term lightly by the way.

While Gladiator has some major historical flaws, I did find it entertaining, which I suppose is the point. Braveheart has its flaws too, but again it was enjoyable enough for me to overlook that. Which was more inaccurate? I'd say Gladiator, but Roman History is my thing, not British history. Ask a Medieval English historian the same question and you'll likely get a different response.

As for other really historically inaccurate films:
300
Kingdom of Heaven (also curtesy of Mr. Scott)
King Arthur
The Last Legion (perhaps the worst ever)
Most "sword and sandal" movies of the 60s
Caligula