I have used lots of options...
...such as Ubuntu since version 6, Suse, Knoppix, Puppy, Slack, Fedora, Mandrake, Mandriva, etc. Yes many of those are truly excellent but the masses of problems that I had getting basic things like monitors, printers and wifi to work over the years was simply too much effort for me and most other people simply gave up for sure!
As I said, place someone in front of linux desktop and most users will be impressed with the familiarity yet more initial simplicity that Windows, at least before KDE 4 and Gnome 3. But when the problems and bugs hit, or want to "install" their favourite app or use a printer not listed, and they are left on their own and get frustrated and fall back to Windows familiarity. Fully supported, then they are happier.
I agree that far more users should be using linux but they are not, for various reasons, mainly unfamiliarity and competition from Apple etc. But linux has a great future with Android and perhaps other distributions, but it will take more time and we are not there yet. All the squabling between various linux "factions" also does not help and diverts development efforts into a high quality product - Ubuntu has realised this and I wish them good luck, but I think their money may run out soon, although I hope not.