It doesn't matter what you use... if it's out of date it's vulnerable. As for which is more secure, again it's all abou the user. The biggest threat is what the person in front of the keyboard is going to do. Saying that Windows gets viruses because people surf to sites with viruses is like saying a car runs out of gas when I turn it on and run it. The "typical" home user isn't nearly as careful about security as say an IT pro might be. It makes sense that no matter what they use, those platforms would experience higher than average levels of infection and issues, regardless of who made the OS.
Looking through vulnerability databases I work with, Windows does indeed have far more, but then again, linux hasn't gone through the same scrutiny. As more and more agencies start using it, it's going to be poured through just like Windows, who actually develops code with NSA involvement. Everytime a new update comes out, there are more and more linux and Apache vulnerabilities, just like Windows. Also, this has more to do I think with desktop OS's. Server 2008 is a vast improvement security wise, at least for now, I'm sure we'll see a lot of things come out about it as well, but it was by far the easiest OS to setup out of the box from a security standpoint than 2000 or 03 were.
So yes, 2002 may want it's arguement back, but it's still relevant, regardless of wether you think it is or not.