Like Peter said, making the two versions identical in regaurds to mutliplayer IS the problem. And letting steam chose the rest of the people you play with is a big deal to many, including me.
Sure, you can invite friends to play with. But unless you fill up the maximum number of players allowed in a game, people you don't know are going to be playing with you. And from what I've read, the maximum number of players allowed in a game is 16. While that may not be unchanged from previous console versions of COD games, it is down from 64 on PC versions of past COD games.
There are a lot more server options that were lost with this released. And since multiplayer makes or breaks these games for a large number of people, Infinity Ward is losing sales. I love one on ones with my friends. Its bragging rights and I love the competition. Now the only way I can do this is having certain friends travel hours to play. Sorry but none of us want to drive hours to do so.
Even if Infinity Ward did all the research and found the potential lost of sales wouldn't outweight overall profit, I believe staying loyal to your customers should have weighed more. And the petition for dedicated servers on COD:MW2 is over 200,000 now.
Saying "FPS's are just better on console" is an opinion that I, as well as many others i'm sure, will disagree with. Those that do agree probably don't have a computer that can handle the game anyways

For me, controlling my crosshairs is much easier and moving around are a little easier with a keyboard and mouse than a controller. I don't know anyone that would prefer a controller when browsing the internet. I agree that "knife only" servers are kind of dumb. But I have played on "modded" servers in the past (not by choice) and it wasn't bad.