The Escape Artist has done a few posts on this and I haven't spotted this one listed, but having re-watched it the other day, I think the purest FI film goes to, the absolute classic in it's own right:
Watch it again, it deserves it. No lifestyle inflation, has trusted friends and positive, after a while, influencing people in his life. Rich, but still takes the bus... he even cuts the grass for free because he enjoys the work!
Honourable mentions to A Good Year and The Family Man, but Forrest has it down for me!