The duels in Empire Strikes Back and Return of the Jedi were grander but still had a sense of realism, while the prequels turned the lightsaber fight scenes into over-choreographed spectacles. They became more about acrobatic dances than swordfights. It seemed as if George Lucas and his fight choreographers were trying to add as many gymnastic flips and somersaults as they could come up with rather than showcase a believable battle within the story they were trying to tell.
In A New Hope, Obi-Wan Kenobi was an aged master, facing his one-time pupil. The slow pace and deliberate motions were suitable for the character at that point of the saga. Watching that duel when we were kids made my friends and me want to be Jedi Knights, noble characters of dignity and honor. Watching the duels in the prequel movies makes kids want to grab a lightsaber and become baton-twirlers. Hey, there's nothing wrong with baton-twirlers, I just cannot imagine a Jedi Knight or a Sith Lord spending hours practicing to spin their lightsabers or to learn moves that more closely resemble a theatrical dance number rather than manuevers for mortal combat or self defense.
Also, the scene in A New Hope, like the finest battle scenes in any other work of fiction, is loaded with subtext that adds depth to the conflict. The lines of dialogue between Kenobi and Vader are memorable because they add drama and tension, making each swing and clash of the lightsabers, each attack and block and counterattack, all the more exciting for the audience to watch.
It is not about rating the opponents on their acrobatic steps, but on connecting with the story of why these characters are fighting in the first place. Without that connection we are just watching a dance routine -- which can still entertain us, but it has no dramatic gravitas to make us care for the outcome in the battle between protaganist and antagonist.
So watch that first Star Wars film again see the greatest lightsaber duel of them all in all its brilliant simplicity.