I was in Grade 12, and went to the bathroom near my biology class and on way back I saw through the door of my Grade 11 chemistry teachers' class and he had his Xbox hooked up to the class television, and while his students were just reading their textbooks and working, he was playing through Cairo Station and Outskirts. I must've been standing there for a good ten minutes because I couldn't play on launch day till school was over and he had already bought it and was playing it. He finally saw me in the hall and yelled at me to go back to my class. That was the draw of Halo 2 back then. That even teachers would go out and buy the game early, and play it in class in front of students.
That teacher was a huge fan as well, he'd often times hook his Xbox up during or after class and have multiplayer matches in CE. I don't know if he ever bought Halo 3. His gamertag didn't seem to be updated when Xbox 360 came out and I was already in university and he became assistant principal elsewhere.