In terms of monthly sales the PlayStation line has managed to surpass the Nintendo Switch which is impressive seeing how fast the Switch console has been flying off of shovels since its release back in March 2017. In terms of overall console sales the PS4 has reportedly sold shipped 60 million units worldwide in 2017 alone so far. There were so many cool games that were featured on the PS4 such Injustice 2, Horizon Zero Dawn, Overwatch and Gran Theft Auto V that were considered to be the best selling titles for that console back in May.
As far as Sony having the best selling console for the month of Nay it looks like sales are only going to get better as the year progresses. We are still waiting for the release of the PlayStation which is expected to take place in 2017.