Good question, I dont have the data on me anymore (I extrapolated it from Steamspy, and I don't subscribe to it anymore). To get a (potentially) more accurate picture, I would instead look at all games that sold more than X units. I think if a game sells about 20k units, its probably a more serious contender (not that some good games have not had extremely poor sales).

Problem with that is everyone thinks they are in the top 20%, by definition they likely aren't.

I think if you're spending 1+ year developing something, even if you start as a complete beginner, you're going to be in the 20% of games on Steam.

There is simply so much shovelware/copy and paste games.