I don't think The Witcher series naturally grew. Barely anyone played the first, only a handful played the second. When the 3rd was shown off at E3, it got a public buzz and alot of hype.
The first game was terrible, the second game was just okay but some parts - like the invisible walls and children speaking with adult voices.
The Witcher 3 is nearly a perfect action rpg though, it seems to me that CD Projekt Red got lucky, because The Witcher 1 and 2 were less than average.
Of course, I own all 3 and have completed each of them more than once.
Do I think that PoE has the chance to become as big? Hmmm... maybe. The thing is that alot of people don't like real-time with pause games anymore, they would rather play something a bit more "accessible" and in your face like but then, Crpg's seem to be coming back in a big way so it might generate some waves of love for PoE in the future, years after the rest of us have already played the games.