tip: it doesn't matter how many votes we get, it's how quickly we get them. notice how all of the quickly popular games got greenlit? there's a reason for that.
There's probably a balance between the two.
It would make no sense to say that a game that can accumulate hundreds of thousands of votes isn't worth greenlighting just because it earnt them over a larger period of time.
It's still obviously commercially viable.
But rate of votes is also quite important.
It depends what Valve is more interested in. Quick money from rapidly growing games, or money overtime from slower, more popular games. They're smart enough to decide to go for both, I'm sure.