He is right.
Windows XP is one of the most loved Operating systems of all time, and after the Vista disaster, Windows 7 was a breath of fresh air, and despite the fact it was rushed to market, it eventually became a VERY efficient Operating System by almost anyone's standards.
I disagree with the inclusion of Windows 8, seeing as how it has yet to be released. If it took Windows 7 two years to get right, so to hold Windows 8 to any standards while it's still in the testing phase is naive.
Other than that, Windows Vista and Windows Me are the two worst Operating Systems of all time, and that's according to the general consensus.
Are you 12?