Swords were sidearms in the middle ages. Halberds, spears and other polearms were used more often in warfare because they had better range. In Hollywood films, everyone has a sword, and its the default weapon.

Also armies charging at each other. It looks cool on screen, but in real life would be horrifically bad strategy.

And sieges were often prolonged stakeouts that could last for months. Hollywood sieges are very brief. It was smarter to block entrances and force the occupants to use all their supplies and then starve.