It depends on the program you are trying to develop. If you are trying to develop a typical business application 10 good developers could probably accomplish as

It depends on the program you are trying to develop. If you are trying to develop a typical business application 10 good developers could probably accomplish as much or more than John Carmack. But if you are trying to develop a game, even 1000 good programmers could not together accomplish what John Carmack could accomplish single handedly.