"How do you define "succeed"? Does something only succeed if it has the largest market share?" -- no: mainly if it's better suited to the task at hand.

"There are many other exceptions: Wikipedia is open source."

Which doesn't matter at all, the success of Wikipedia is in the content and the participation of the content creators, not in the open source-ness of the underlying wiki engine.

"And don't forget OSX is based on an open source kernel."

I don't. But that has nothing to do with the success of OS X. Darwin itself never got anywhere.

"Many tools used regularly by developers are open source."

Yes --but those are not replications of existing closed source ones...