Recently we have seen some STS-like but they are bad copy of the original (visually horrible and bad writing) . Because they want to have success quickly. The first visuals of STS are not as good as they are actually, DC progress in drawing and take more time to do more quality. The quality of the game is the origin of his success.
This is actually the wrong way to look at them honestly.
They came later but the standard has been increased by STS who has a few advantages by working within the game industry (DC's past) and high quality art.
I would just call the "clones" as more niche products that appeal to a smaller audience. Economically speaking, there's a LOT of advantages to being first and a few years back, everyone focused on him right after two fiascos which left him filling a hole no one knew about.
It's the same thing as workplaces using Adobe and Corel being less used. They're still art software, but one is a natural monopoly.
Just my little thoughts on it...
