I haven't touched my ODST disc in over a year. I mainly just use the Mythic disc. It allowed me to delete my maps from my Xbox's HDD, giving me some memory back.
I certainly will not be buying Halo: Combat Evolved Anniversary. When they announced the multiplayer was just going to be stacked on Reach's engine I gave up the thought of purchasing it.
Elites always get my vote in these kind of polls. My least favorite have to be the Skirmishers, great concept and whatnot but when the game lags they become near impossible to kill with the sniper rifle.