Well, actually Isildur is Anakin Skywalker, who in fact didn't die at Gladden Fields like everyone thought, but instead chose the dark side of the force... and so he became the Witch-King of Angmar. Sauron is the Emperor.
Luke is Aragorn, so that makes Arwen Leia... Elrond became her fosterfather, after Obi-Wan/Gandalf took her to Rivendell.
and of course, the cave-troll is Chewie! They don't make the same noises for nothing!
And btw, it's Alderaan.
P.S. : yes, Jar Jar Binks is Faramir. (:-P
Give up the Halfring, she-elf...