Microsoft saying that win2k is not for games, is purely marketing.
They know that Win2k is a very stable Windows platform, but that there is no recurring revenue in that OS. So, unless they push new technologies and quickly quit supporting Win2k, people will have no reason to change to another OS. Specifically XP, which is built around subscription content and media control.
So they simply turn out the marketing team to kill 2K on the desktop, and get it replaced with XP. Saying games are no good on Win2k is part of that.
(oh, and I've never had a problem with Win2k and games, or much else for that matter)