For me, it's what I liked the least.
In the early nineties windows 3.x sucked for gaming, which were 99.9% DOS anyway, so that windows didn't matter much in regards to gaming.

With the coming of Windows 95/98 (I will not even mention ME) everything moved to windows, which was slow, unstable and terrible for gaming until directx5 came along, the frequent crashes were a pain, while gaming with 3d accelerators which were finally widely supported in '97/'98 was a blast.

With Windows 2000/XP the instability period ended. My PC's wouldn't lock up if a game had a bug, so a complete system restart wasn't neccessary every time a game crashed.
Windows 7 is more of an evolution, and a lot of things are easier and more streamlined (I skipped Vista)

I used 95 and 98 only in school, then 2000, XP, Vista and 7 in my own computers. 7 are the best by a long shot.

Started using Windows with the 3.0 release, then ME (...), XP, now Vista, soon 7. Windows 8? NEVER, not even if they pay me.

The best Windows for me? QuickMenu III for DOS+Xtree Pro Gold "4.0" (...). No really, that was a kickass GUI couple :-P

Experienced 3.11, 95, 98 with all of its flavors, ME, XP, Vista, and 7. So far I am leaning towards 7 being the best one for Windows gaming. Heck, I installed Win 7 Ultimate on this netbook and everything seems to be chugging along just fine...for now.

Those I have used a lot of are 3.11, 98 (and SE), 2000, XP, Vista, and 7. I believe that is roughly much my order of "like" as well, from least to most. Unlike many others, I never comprehended what was so horrible about Vista, it seemed to chug along just fine for me.
(I have used the others as well - 1, 2, 95, Me, NT4, servers - but not enough to have much of an opinion of them.)

While I dislike the choice of turning the hierarchical start menu into a "start screen" in 8, the changes made to the desktop experience seem mostly to the better. It might grow on me, or I might skip 8 altogether (probably except for testing) and wait to see what they have in store for 9.

Ran just about every version (with the exception of ME) and supported them all.

Like 7 the best, closely followed by XP, and never paid attention to Windows flavors that had DOS underneath them, as I just stuck with DOS and only loaded the Windows UI for support reasons (so I could walk someone hand-in-hand solving their Win problems.)

Having used all windows including 8 CP, I have to say 7 too and I suspect it will remain 7 for several years.

A DOS is not a Windows!!!

I've experienced Windows 3.0, 3.1, 3.11, Win 95, Win NT, Win 98, Win Me, Win 2000, Win Xp, Win Vista, Win 7.
Still using XP, but preferring Win7. I'm glad that I don't have to go back to the days of Win 3.X (which i never had on a computer that I owned, but my school stuck with Win 3.X on most of its computers up to around 1999).

Windows 7 is by far the best. It's not even a personal opinion. It's a statement of fact.

I've been using Windows since 3.11 and apart from the ones specifically labelled NT or Server I've used them all to some degree or another.

XP is my favourite, although I use 7.

Well, I'm currently using 98SE, XP and 7, and it's a preference issue. Like, for instance, I want to play some Shadow of the Horned Rat, the 98 is the best one, hands down. Oh ha, ha, ha. No, really, W7 all the way.

I've used every consumer release since 3.1 (3.11, 95, 98, 98SE, Me, XP, Vista, 7), along with Server 2003 and 2008 (and WHS 2011). I've also had a bit of time on 2000, but not enough to call myself proficient with it any more than from basic WinOS knowledge. For a long time, XP was my favourite, but since upgrading everything in my house to 7 I find XP so clunky whenever I'm called on to fix it for work or friends and family...

Congratulations for your acumen, Captain Obvious :-P

I didn't dislike Vista so much as many others did. I still have two hosts that are going to finish their useful lives with Vista licenses.

But Windows 7 is mostly improvements, especially in memory management, where Vista is really sloppy.

The one thing I dislike about Windows 7 is that it provides too many ways to exempt installers from popping up code-signing check dialogs. Most people consider them mere annoyances, but I damn well want to know exactly who is vouching for everything I install.

I've also been running Windows 8 CP since it came out. The UI is a Charlie Foxtrot of the worst kind, but otherwise it is very solid, far more so than when any previous Windows came out.

For servers, I regularly use Server 2003 and Server 2008R2. 2008R2 is a pig. For situations where I don't need features that aren't in 2003, I much prefer 2003.