What makes the game enjoyable?

This post has been sat in my head for a couple of days but I think I have finally gotten the right thoughts on the matter to be able to make them into some form of coherent post.
What makes the MMO you play fun? What changes within the game cause it to not be fun?
There are a few factors which can enhance or reduce the “fun” ill list some of which are springing to mind now:

1. Are you playing a character that you enjoy playing? You may think this is a funny point but many people play in a guild where a certain class is required and although not the first choice, you play it anyway to help the guild. Would you be having more fun on the class you want to play? Some would argue yes you would, I used to be in this boat until I changed to play the class I wanted.

2. Are you playing with people you enjoy playing with? This is another fairly big point, are the people you play with fun and enjoyable to game with? This kind of ties in with point number 1 and ill explain below:

I raided for years with The Harpers of Norrath on a class I didn’t really want to be playing. I tried and tried to main change but got turned away every time. But the people in the guild were fun and ive played with them for years, in fact we were in previous guilds together so it was still a laugh.

I got the opportunity to raid on the character I wanted to be playing. So I upped sticks, away from my friends and into a new guild. Do you know what id prefer?
Being with those friends. The class I play now is everything I want it to be and I love it, but the loss of the camaraderie and fun has hit me hard.
The case of the grass is greener? It might be because im now having to integrate myself into a new social group rather than be in my old one or it may have something more.

Ive seen more content now with the new guild than with my old but still unsure as to what id prefer…. Part of me wants to go and be a social in Harpers but I really want to see the raid content come next expansion, I love the lore of Velious and want to see everything I can.
The other part of me knows that in the long run I wont be happy with non raider status in Harpers.

Just one of those situations where you need to figure out whats going on!

Id be interested in points of view of what makes the game enjoyable for others?