This is a late post, obviously, but I do see where you're coming with your post-mortem of sorts.
I bought the 360 in June of 2006, ironically for Battlefield Modern Combat. BMC was your Gears of War 3 to me. I played the living hell out of that game, and learned every map (anyone remember Bridge Too Far?). From there, I went on to games like Call of Duty 2, Gears of War, and others, all the while appreciating the 360 more and more. Combined with a Gamefly subscription, I had endless fun with that machine. That is until I built myself a gaming computer in December of 2010.
I cancelled the Gamefly membership, took advantage of Steam sales (when they were still unbeatable), and got into TF2, like you. The 360 became more of a Netflix and HBO Go system that a gaming machine, and for the most part, it still is. It's unfortunate, really, because the system used to be such a technological advance, at least in my eyes. I remember going to Gamestop in 2005 to play the Call of Duty 2 demo they had set up, and I remember just marveling at how life-like the game felt. I guess we all get a bit sentimental at the end of a console's lifespan, but out of all the consoles I've owned, the 360 is the one that sticks with me the most. My only hope is that they don't ruin the 720, as the gaming community seems to predict they will.