I think that special consideration should be given here to multiplayer games that don't have carryover here. Games like Pit Stop were obviously designed as two player games.
Quoted from EMsInKC:A bad game is a bad game and won't be made any better by adding players to it.
Having multiple players can change the dynamic of a game completely. Just having more people gathered around watching and reacting can change stuff. A lot of more luck based games can be improved especially.