XP had its issues, like every OS, but compared to having to run the OS on top of DOS like Windows was previously doing it was a huge improvement.
Windows 2000 was not based on Windows 9x, so did not run on top of DOS. It was instead an upgrade to Windows NT 4, with some added integration to allow Windows 9x programs to run, so it was the first OS that unified both the enterprise branch (NT) and consumer branch (9x) of Windows. So Windows XP was not new in that regard. Think of XP as Windows 2002, or Windows 2000 with a candy-like interface on top and a few other improvements. Here's an NT history for reference, showing the version progression from NT 3.1 up to Windows 10: http://en.wikipedia.org/wiki/W...
The Windows 8 improvements over 7 are worth it. Speed and security to name a couple. Especially when you consider that if you really can't handle the interface you can easily download free utilities to make it look like Windows 7.
The fact is that even though people like to gripe and moan, every version of Windows on the NT branch as outlined in the Wikipedia article above has been an improvement over the previous version.