The kind of people who entertain me are the kind of people who are highly empathic and highly sharing. I mean a social gathering isn't fun if one person is dominating the scene by "being an entertainer". A social gathering is fun when everyone is sharing in the fun because everyone understands the give and take, the flow of the conversation, the mood of the room. My good friends are entertained by in-jokes and _shared_ silliness and we don't depend on any subset of us to create the fun, we create it together.
So my friends are all entertaining but not because they are self-centered entertainers. They are entertaining because they are the kind of people who are down to earth and honest and would always be there for you when you need it. Put a bunch of those people together in a room together and good content easy going fun times are had by all. The self-centered egomaniac "performer" types drive me nuts and I don't put much effort into spending time with them.
And I think the whole process feeds itself. I think people are more likely to "be there" for people they've shared a lot of positive (entertaining) social interaction with. And people are more open and comfortable with themselves (entertaining) when they are with people that they know they can trust.