After last night, I have an understanding of the elitist Halo 1 players. I dug back through the site to find "Reasons that Halo can't possibly be better than Halo 2".
It really is a matter of comfort level. Demo and I were discussing how Halo 3 seems to play so much slower than Halo 2. After popping H2 in and waiting an eternity to download all the maps again, we found that it was true. MC moves much faster in Halo 2...and every movement seems critical. Halo 3 has lost some intensity, although the game itself is much more fair in the battlefield than its predecessor. Any lag can be crippling, and even slightly missing one shot is the end of your life.
Overall, I can honestly say that H3 is the better game. But to get the heart pumping again...I gotta get that H2 fix once in a while. :)