It you want some motivation or some good watching then buy "Pumping Iron (25th Anniversary Special Edition)". The extra footage included is exciting enough.
Here's some others that I always watch and hasn't been mentioned:
- Lee Haney's Mr Olympia Workout
- Arnold Schwarzenegger Total Rebuild: The way to Mr.Olympia 1980
- Lee Priest: Another Blonde Myth
- Shawn Ray: Final Countdown
And the one's that have been mentioned:
The Unbelievable & Cost of Redemtion with Ronnie Coleman are very impressive and exciting to watch as well.
My best choice overall is Pumping Iron though.