Well Vista was a flop so I guess the last decent Windows OS people remember was XP. I used that up until Windows 7. I've heard Windows 8 is horrible. But, Windows 7 is much better than Vista and has been out for a while and is more reliable and stable now than at release.
Comparing the two doesn't make much sense, since one was made with the purpose in mind of improving everything wrong with the other. I got a lot of good years out of Windows XP, but after using 7, XP seems basically obsolete.
I use Skype from time to time to talk to my cousin. He's hilarious, but I don't see him very often in person. I suppose Yahoo messenger also has a video chat feature, but everyone I know uses Skype. In fact, they don't use Skype--they Skype. It has its own verb. Clearly superior.