There are many, many rules laid out for putting on a perfect dinner party. You've got to have a great spread, naturally, with all sorts of exotic cuisine ready to be devoured by the eager participants. Fine wines and hard drinking is a plus too. Some even descend into lewder shenanigans if you live in certain suburbs and own enough lubricant.
But ask any PC gamer who was around at the beginning of the CD-ROM revolution and you'll get one answer about what makes a perfect party. You've got to have a 7th Guest.