Good luck with the treatment, sorry to hear about your condition. I'd second many of these films, here's a few more:
The classics:
Casablanca, African Queen, Lawrence of Arabia, Harvey
Man in the Grey Flannel Suit, Rear Window, Vertigo
Comedy:
Blazing Saddles, Young Frankenstein, Pink Panther series
Black Comedy:
Full Metal Jacket, Dr. Strangelove, Kind Hearts and Coronets
Action:
The Professional, Run Lola Run, The Fifth Element
War:
The Longest Day, A Bridge Too Far, Paths to Glory, Mr. Roberts, Patton, Battle of Britain
Underrated:
Little Miss Sunshine, Kiss Kiss Bang Bang, Red Rock West
Definitely No Country for Old Men and HBO's Rome too - both were awesome. I added Rome to my Netflix queue. Maybe the new Battlestar Galactica?