My vote goes to High Fidelity. This movie always amazes me. If you ever lose your compass and need help finding out what is important, this movie can help. (At least it helps me.) Love and music can help most human conditions!
I am very surprised that no one has listed 'The Big Lebowski' yet. As much press as that movie gets around here, it has to be on someone's desert island list.
Probably In The Mood For Love Criterion.....or Fellowship Extended. Both of these sets feature first rate films, along with a plethora of quality extras.
If, when The Magnificent Ambersons comes out on DVD, they've miraculously dug up the original version from somewhere, I'll take that instead, without a shadow of doubt.
Oops. I looked at your list but not the text of your original post. TBL is one of my favorite films and would definitely go to the island with me. If you look at it critically, TBL is not one of the greatest movies but there are so many lines that just hang in your brain for months after you watch it. Just priceless!