Tastes vary and I can't take you to task for your characterization of what is my personal favorite film. I have a very long attention span and can stay focused on a compelling film (or book, take Mann's "The Magic Mountain" for example) that others may find overly long (such as Judgment at Nuremberg and Lawrence of Arabia, two other favorites).
The only movies I truly dreaded -- where the minutes dripped by like hours -- were The Matrix and Lord of the Rings. I had to watch them at a colleague's home as part of dinner and movie. Being polite, I feigned interest but it was hard to stifle my yawns through the near torture of that fare.
I was younger at the time I watched it, and I think my experience was somewhat sabotaged by always hearing of it being “the best movie of all time”. I’m sure you know how the expectations thing goes when it comes to movies.