It isn't better. You can argue with me that it is "free" and "open". But that doesn't mean enough.

1) "When Windows breaks I have to reinstall - you can fix Linux." - I agree but there is a limitation. Linux breaks in some ways just as much as Windows and yes, you can fix it. However:
a) it shouldn't just break (which it does)
b) I waste a lot of time "fixing" it and
c) the best option (and safest) is often to reinstall when things really do break

2) It is a hobbyist OS. Yes, you can do all sorts of cools things and all sorts of tools are on it. That doesn't really help me when I have some specific tasks to get done that are part of the Windows world. We live in a Windows world.

3) Linux is not going to win any OS war (it was never in it either). It isn't ready for mainstream. Don't give me your Ubuntu arguments - Ubuntu lags behind and is just as much of a pain as any other distro. Not to mention that it has taken the useful parts of Linux and hurt them by having older, "stable" packages. No, Linux is not just ignored because people think it is too hard to use. It is ignored because it is hard to use. See point 1

4) Windows isn't as bad as you want it to be. Every few releases, yes Microsoft releases some god-awful Windows version but they are quick to market with a better one (yes, I know you have to pay money). But let's discuss this, if you thought that Gnome, KDE, XFCE, Fluxbox (etc.) were not good window managers, or that ext2/3/4 was a poor performer in Linux you'd be told to make your own and how it was better than the Windows equivalent regardless of the flaws you had noticed. And when things get bad (and I consider KDE and Gnome to be bad in their own ways) you just have to wait for time to pass and hope someone out there listens...money isn't steering the development and that means there is no real reason to fix a flaw in the next major version.

5) Virtualization - I spent a lot of time with KVM, Xen, Hyper-V, and now VMware. KVM and Xen are basically in the same ship and are too young and incapable for real use. Hyper-V and VMware solutions are more appropriate in terms of "real" use. KVM/Xen, where is good snapshot management? I'm using VMware ESXi - somewhat Linux, yes. Specially designed for VMware virtualization and nothing like Linux distros? Yes

I could go on, but my main point is that Linux is not really good about just working (any more so than Windows, anyway). I'm tired of fixing my OS - I know how to not destroy Windows (I'm looking at people who "magically" or "accidentally" get viruses).