Comparing this with Excalibur and other Arthurian movies
One thing I liked about this film was the more or less historical costumes. In Excalibur, you could forgive Boorman for using anachronistic plate armor because he was being faithful to Malory, one of his sources. Here, it was refreshing to see pseudo-Roman and Celtic costumes -or at least it seemed.
And I noticed that some parts of the storyline seem to have been directly influenced by Excalibur!
-In Excalibur, Merlin gives Excalibur to Uther so that he can become king and stop fighting with Cornwall. Later he tells him that he's not the king who will unite the land, as he had hoped. Still later, Uther drives Excalibur into a rock after he is ambushed by enemies, and dies.
-In Merlin, Merlin gives Excalibur to Uther after his battle with Vortigern. Later he tells him that he's not the king who will unite the land, as he had hoped. He himself drives Excalibur into the rock. Uther later commits suicide.
In both versions, Excalibur and the Sword in the Stone are one and the same.
-In Excalibur, Arthur attacks the forces of Lot and Uryens, who are besieging the castle of Leondegrance, Guinevere's father. He disarms Uryens in combat, and tells him that he will spare his life - if he swears faith to him. Uryens refuses, for Arthur is not yet a knight, and it would be shameful for a great lord to surrender to a squire. Arthur then hands Excalibur to Uryens and tells him to knight him! Uryens is tempted to strike Arthur down and keep the sword. But he relents, dubs Arthur knight and swears fealty to him, impressed by Arthur's courage, which he got from his father Uther.
-In Merlin, Lot does not recognize Arthur as the rightful king. This leads to war. Before their forces fight, however, Arthur tells Lot to strike him down with Excalibur, if he thinks he is the true king. Lot relents, influnced by the magic of Excalibur (Right?).
One thing I didn't like in Merlin was its putting John Gielgud in the opening credits when his character was in the story for about 10 seconds or less. After that, he gets killed by Vortigern.