Even after playing mw1 and enjoying it thoroughly, I would still place my bet on ww2 setting. First, I am personally fascinated by it and I love to read about it and second, the arcadish feeling in the first few games was something else for me.

Am I the only one that immediately thinks "MechWarrior" when people abbreviate "Modern Warfare" and has to back up a few words and try again?

That just means you're old :read: (I do the same)

Creating a modern-themed game is easier than ww2-themed games for the developers. You have many freedom while making modern-themed game. You can make your own story, make the setting of the game of your choice.