My opinion on people who have the same favorite CoD as I do: People who know a well polished game when they see one. People who don't complain about the game when they get killed, but rather, complain about their own lack of strategy at the time.
Opinions about other people who prefer other CoD's
Cod4: For the most part, people who are overly nostalgic about their "first love." That's what I typically see. But Cod4 is my second favorite Cod, so I see why many people still prefer it. It ran smoother than anything after MW2, and was a fairly simple CoD.
Waw: I don't see how people can like this game unless it was their first CoD. It is easily the laggiest experience I have ever played in a CoD game. The only redeeming quality in the game is the scopeless bolt action rifles. Other than that, Cod4 is better in every single way.
BO This game was an "ok" experience at best. Like many others, I thought it was good, but it got boring way too fast. It wasn't a very exciting game at all for me. I personally think people who prefer this game only like it because they couldn't keep up in MW2. There are simply less things to complain about in BO just because the game took on a stripped down approach in my opinion.
MW3 People actually prefer this game? I can only imagine people preferring this game when it was in its peak.
BO2 I think people who prefer this game only like it because it's the new CoD out. I'm going to wager that the same people who prefer this game are also the same people who will hate it and bash on it once the new CoD comes around.