I don't doubt that Steam being first to market is the biggest reason for their success, but you make it sound as if there's some alternative store that is better for the consumer in some way. What's the alternative? I have yet to see any other store/launcher come close to Steam in terms of features, even more so when it comes to Linux support, which Valve have turned into a viable gaming OS pretty much by themselves. In the end, even exclusivity and drastically lower fees for publishers didn't make EGS the success that Tim Sweeney wishes it was and I think at that point being first to market can't be the only explanation. They have to be doing something right.