When Windows XP first came out, we were all living with 98 and 95 which were not very dissimilar in appearance to each other. The world (or rather, me) didn't really have much of an idea of what to expect other than a new OS. But when XP came out, I was awestruck. The blue taskbar, the green Start button! Everything was amazing!
The same thing happened with Vista. Transparent taskbar and windows?! How? How much processing power is being wasted for these effects I thought then. But Vista was beautiful, at least when comparing it to XP. It was, I'd say, a beautiful cousin of XP because the underlying mechanics were similar. The "killer" feature was the Windows Aero, the feature that was to cure cancer. However, it was not to be, and it turned out to be just an over-glorified task switcher that hardly anyone uses because it is redundant due to the existing Alt-Tab switcher which works sufficiently well.
When 7 came out, I laughed. I was a Vista user at the time (and I still am). 7 seemed more like a tweaked Vista at the time and never gave it its due credit. However, after using 7 for a while, I have come to appreciate its many feature additions compared to Vista. I'd say, 7 is the best OS out of the Microsoft stable.
When 8 came out, I was not convinced. I liked the idea, seamless experience between phone, tablet and desktop/laptop. But the desktop version is half baked. It's halfway from 7 and the future. It's neither here nor there. The desktop is all 7-ish, but some parts of it have not been done right. Probably my views on 8 will change if I use it extensively like it did with 7. But for now, I would rather bet on Windows 10.
I guess the feedback for 8 was so bad that Microsoft even skipped a whole version number and jumped straight to 10 from 8. Exciting times are ahead of us.
Follow this link for some preview images from the yet to be released Windows 10. Link