That's not his call, or anyone else's, but that of the market as a whole. There are few if any artificial barriers to success for a prospective competitor, except for their own unbridled greed and indifference to customer service.

In the technology sector, the greatest success stories have emerged not when one company executes flawlessly, but when one company executes competently in an environment where all of the other competitors act like barking idiots. You can't even count the number of times this has happened, but citing Microsoft, Google, and Apple should be enough to get the point across.

That's what's happening with Valve, IMHO. It's not that they are perfect... but when your competition is Electronic Arts, it's hard not to look good.