I liked both the above movies. No, actually, I out and out loved Fahrenheit 911. Sad that it only preached to the saved.
We watched Day After Tomorrow and loved it. It was thoroughly panned by the critics, I think they wanted it to be a more serious look at what we're doing to the environment and instead it was just a classic, fun, cheesy disaster flick.
Good special effects, and although long did not seem too long at all. It did, however, lack the two absolute requirements of any truly cheesy end-of-the-world disaster flick, the Golden Gate Bridge has to get it, and the solution to whatever is destroying the earth must be fixed with a nuclear device (classically killing off a main character who must be at Ground Zero at time of detonation).