I don't necessarily think about whether I would want to spend time with my characters at a party, and I think that if that was literally what was meant, it would be a pretty ridiculous measuring stick of character value. I do, however, agree wholeheartedly with what I think was the more general
point Mr. Gaiman was making - the most important thing you want your characters to be is interesting.
How does your opinion of your characters affect your narrative, if it has any effect at all?
Now this, I do have strong feelings on. I am decidedly against letting one's opinion of one's characters impact the story in any way. From my strong Watsonian
point of view, I get the idea that the writer should think of themselves as a chronicler of "real" events - in other words, I Just Write the Thing
. This means that your opinion of your characters should not affect their fates any more then your opinion of some historical figure should be able to change the past.
From a less philosophical standpoint, either overtly liking or overtly disliking a character, and letting that come out in the work, tends to lead to poor writing - for instance, see The Wesley
. I therefore think it's best to try and leave your feelings about your characters out of writing altogether. Let the readers decide for themselves.
That doesn't mean you can't have favorites among your characters - but don't let that influence the work in any way. And, of course, your characters can and should very much have opinions about other characters in the work. Just keep them distinct from yours.