and
it becomes clear during the game that the setup is bad. (Note that even a massively unbalanced setup can be fun to play if you don't realise it until the game is over.)A game generally also sucks if the playerlist is bad, something which always becomes clear during the game itself (if the dayplay goes fine, it wasn't a bad playerlist).
As such, I would guess that playerlist is more important than setup, but both are somewhat important.