I posted the following in another thread, but it's relevant here and it helps disprove your theory even more:
I've ran multiple tests loading both games right after another. The actual population of players in matchmaking has been higher in Ghosts every single time HOWEVER the menu population has been higher in Black Ops 2. Black Ops 2 just now said 140k online, but only 73k when you combine all public + league play. Ghosts said 130k online, but over 115k were in matchmaking. This shows that far more people are playing Ghosts multiplayer than Black Ops 2 on 360 alone. Keep in mind that there are still four cods in the top 10 and five in the top 20 on xbox live so it's not surprising that Black Ops 2 is still doing strong.
I just took another test and now have video evidence (uploading to youtube) and a rewrite of this comment are coming.