I've heard an unsubstantiated rumor that a patch is coming for Call of Duty 2 on Xbox 360 that will bring, among other things, 16 player games and a fix for the lag issues. From what I understand, the patch itself is nearly complete, but it's a month off or so based on testing and certification.
COD2 should be the killer 360 game - but the lag is so bad right now that I've almost stopped playing entirely. If they can fix this - and increase the size of the battles at the same time - that's great news.
I've heard similar rumors about a Madden patch, although I don't know what's supposed to be included in that. There's enough missing in this version so we'll see what they decide to tackle first. I would love to see some online leagues with a built-in storyline central... but that might have to wait until 2007.
Update: I originally heard this from an IW employee, but it turns out it wasn't just an unsubstantiated rumor. Given the "official" announcement, it seems likely that the timeframe I mentioned is reasonable.
Update #2: The patch has apparently been done for awhile, but is still in test and certification processes. Complicating the matter is some beauracracy considering this is the first game patch to be deployed.