I maintain that in most cases, the classiest way is a simple alphabetical list of people who contributed to the project, possibly broken out into two or three sections ("team members", "contributors", etc). That's essentially what Valve does, and it creates the fewest fights. Except, of course, that some people think they don't get enough credit that way and insist on being special listed.
At the end of the day, nobody has cared about your exact listing on a credits screen in decades. It's a largely self serving piece of the game.