I loved Halo 2. Out of all the Halo games I still believe that was the best one. The points they make in that documentary change nothing about it, and to be frank they didn't look like they were otherwise smart and skillful players.
People can complain about the lag (really, that's the cause of most of the crap the way I look at it), the mods, the weapons, what is overpowered and what isn't - but the truth is that people 9 out of 10 times only complain when they lose. Besides, there is lag, mods, cheats and overpowered weapons in every game. If you can't beat it, use it.
Looking back at the hundreds if not thousands of hours I played Halo 2, I think it's safe to say I haven't enjoyed any game the way I enjoyed Halo 2.
We can keep arguing though, and nobody is going to change their minds. It's a matter of personal preference, as with anything. We have Reach now, so let's just stick to enjoying that.