The gaming industry is way ahead of music, movies, books, and TV. About time.
The game isn't necessarily that great (I'm very familiar with the games industry and especially the Call of Duty franchise) but Infinity Ward knows their market and how to appeal to their consumer-base better than
any pop star ever could. I'm referring to the number of copies sold rather than the gross, but considering games are 6x the price of an average album, that's nothing to scoff at.