Rainbow Six Vegas 2 still has an incredibly loyal following considering the number of shooters that have come out since. Personally I still rate it as one of the best FPS's on the 360, as far as core gameplay over presentation goes, but was amazed after jumping on recently that people are still on going hard as ever on Terrorist Hunt.
Really had some fun times with the very strong Australian community always on in the evenings and ended up befriending several guys out of it.
Funny thing is that since everyone maxed out the highest ranking long ago, and in the absence of 'prestiging' players on there just have obscenely high '[Insert number of ranks above Elite]' next to their names.