There are too many script kiddies out there that just want to prove that they can get into your system. Many of them don't intend any more damage than that.
And since there are plenty of exploits that only exist on Windows, I think we'll likely see more e-mail virii (and hoxes) etc.
There is no need in arguing what's better or what's worse. Hackers are always gonna go after the top dog for their tricks. Therefore, IE-Outlook and Windows itself will be targets for quite some time. It's not necessarily Microsoft's fault. They've given us user many more avenues to do the things we do. They can't possibly prepare of every exploit that never existed before their software was released. It may suck, but the hest we can hope for is that they continue to work to close up some of those holes.
If any other app/OS becomes more popular than an MS offering, you can rest assured that the hackers will go after those as well.
-SUO