Here's a riddle for you - what's different about Bush's "Either you are with us, or you are with the terrorists." and Vader's "If you're not with me, you're my enemy."?
This is not the only comparison political activists have drawn between the two "leaders of the world". Some like it, some don't - they feel that the movie is unpatriotic and should be banned at all.
However, according to Lucas, the script was written long time ago and if it really does leave a rather "funny" impression of Bush, this wasn't intended and this is just a coincident. We believe that, but do you?
One way or another, Revenge Of The Sith is definitely one of the best movies around.