Well I think in the case of WOW its an experience that can provide many different things. When it came out its world was quite beautiful- there are lots of interesting places to explore, and secrets to find.

I am the only one that feels TES is better suited to a small co-op mode (4 buds playing Skyrim in the same world, allowed to explore at will no matter how far apart they grow) as opposed to full blown MMO? Maybe it's just because I'm not an MMO fan, but I feel like that would be better

The latter. The former is a power fantasy for men, and the latter is a sexual fantasy for men.