I can think of about a hundred logical flaws in your line of thinking--like touting the Orange Box for Team Fortress and not even playing the multiplayer in Halo 3, or praising Halflife for it's "high standard of visual design and pacing" even though it looks like busy, last-gen crap (ironically filtered in the coffee filter lens you so adamantly crusade against in all of your other reviews). You should stick to critiquing and stop PC/Valve pandering that makes some of your reviews so droll and boring.
Having played both, he is not missing much with Halo 3 MP. It has its moments, but the biggest hiderance may be in its console interface (lack of a server list, etc). Unfortunately, that is also a weakness of L4D. I still fail to see why you cannot go to a server and join it, and not have to deal with the game "searcing for server" to host your game on. Lack of control!
Anyway, i agree with much of what he said. A lot of the things that I find lacking, and enjoyable about the game are just what he said. It FEELS like the new era of sprinting-bloodthirsty zombie fliks that have come out in the past few years.
Also, Co-op is where it is at. If you do not play tight with your teammates, it just is not fun! This game needs people that are at least WILLING to play with each other, and Steam really helps with that!
From all the people that played TF2 that were looking for something a bit different, this is it. The only real weakness being the lack of levels to play, which, as has been shown with the patches for TF2 - PC, may be amended in the near future with some new levels, critters, weapons, or modes.
I also find it hard to justify $50 for, but that is what you get with a credit card, a free demo and a few whiskeys!!!