Well, to be fair MS has never been "on top" per se.
Anyway, to answer the question I'm going to vote MS despite not being the market leader. But this is with very limited data. MS botched the Xbox One launch HARD. Now, Nintendo faltered with the Wii U, but it was more because of an inability to advertise correctly and a misunderstanding of market direction. Sony botched the PS3 launch, but that was mostly because of the hardware they were trying to sell (they launched with full BC and everything). MS is really the only one that I feel was truly complacent.