Episode IV: A New Hope
Quite possibly the most recognizable robot in cinema history, we all fell in love with R2 the second he rolled out with his constant companion, C-3PO, and into our hearts.
Also, I've always thought he was a humorous character, but it wasn't until I watched the original trilogy again this week (in anticipation for The Force Awakens) that I realized just how witty and clever he truly is. I also forgot just how much he goes through in those films: he gets shot in the attack on the Death Star and at Endor, and he gets attacked by a swamp creature on Dagobah. Plus Yoda hits him with his cane for trying to steal his food, which he already stole from Luke.
It's almost unfair to put R2 on here without 3PO, but I'm already going to cheat a few posts down the line. The two really add a sense of wonder to the series, and I can imagine R2-D2 may have been higher on this list had I made it about 20 years ago.
"But I was going into Tosche Station to pick up some power converters!"
Luke is the main character of the original Star Wars trilogy, but that still doesn't get him higher than number 9 on my list. Despite how much he does to destroy the empire, I can't quite get over him being a whiny teenager for a lot of the movies.
He totally redeems himself in Return of the Jedi though, because now he has finished training, and is ready to kick butt.
Watching him develop from teen that knows nothing about the galaxy, to force weilding Jedi that defeats the empire is a fun transition to watch.
What his role will be in the new film I have no idea, but I can believe the current speculations of him falling to the dark side. If he does I can see that making sense. (Luke left Yoda in "Empire" when he was told not to. This could have easily left Luke without the proper training that would make him good forever.) Well enough speculation luke was pretty cool in the original trilogy, and that's why he comes in at number 9.
I'm not going to go long on most of these unless I think it warrants it because the character is relatively minor in their movie role. For the most part, everyone knows these characters. Sooo.... intelligence + leadership + bravery + beauty + fighter = Amidala