That's not a very interesting observation. Part of the reason that successful open source projects are, presumably, statistically far less than unsuccessful ones is that the barrier to entry in order to start an open source project is basically non-existant.
Any 12 year old who gets an idea for a game can put up a project on sourceforge. However, proprietary software has steeper barrier. Typically, it comes from people in an established company if not an entrenched bureaucracy.
It's more interesting to choose projects that have achieved certain milestones (beyond one man-week of labor as you put it).
As well, there are plenty of proprietary projects that have failed and you have never heard of and never will. Data about failed proprietary projects is much more difficult to find. However, open source projects are almost entirely transparent about that kind of thing.