College-aged kids were not playing Halo 3: ODST over MW2 in 2009. It was my freshman year. 95% of people were playing MW2, with 4% playing W@W Zombies.
The following year in 2010 it was Reach for about a month after it came out but then quickly became like 90-10 CoD to Halo again.
If I'm being extremely optimistic I could blame some of that on Reach playing the way it did but the real truth is people just preferred the constant dopamine unlock and upgrade system CoD offered.
I don't even remember Halo 4 making a sizable splash at all in 2012. There wasn't even really a line at the local gamestop like there had been before in 2010. There were still more people I knew playing Battlefield 3 from a year earlier than Halo, and obviously 2012 is when Black Ops II came out as the final game in the CoD golden age.
I wish I had gone to college 4 years earlier. It would have been lit going in with Halo 2 and having Halo 3 come out while I'm there.