People need to learn to separate OS stability and third party software issues. Vista had a lot of the latter. As far as the best, that'd be 2000. Not just for stability but the best Windows release period.
It's pretty much just Windows 7 with stability improvements. Sure it has the Metro UI which a lot of people hate, but that's not what the topic is about. I think that a lot of people will just end up picking their favorite OS, though.
I had to leave out some options because GameFAQs is limited to 10 choices. So I decided to leave out the server versions altogether.
Most stable I went with 2000, though I'm not sure about the best. I believe Windows 2000 was sufficiently rushed to be missing some features, msconfig being the first thing that comes to mind (though you can just grab the XP version).
"...Ashley takes on Lord Blazer alone in a white cape with flowing rockstar hair while playing his impossibly cool sword as a guitar..." - LBoksha
I'd say Windows 7. Certainly not Windows Vista. It's probably the least stable out of the whole list when it first came out.
Vista is godlike compared to Windows ME.
Random Crashes, Bugs aplenty, compatibility problems up the wazoo. Even Microsoft just completely gave up on it when it was first released, and didn't even bother to patch up the problems with it, and went straight to developing Windows XP.