I'm not fully aware of all the stuff Ms and Nintendo have planned for 2018, heck I don't think we know about all the games coming for the PS4 either.
But I would say:
1: PS4 (Definitely the king)
2: Switch (With its current sales one can expect 2018 to be fairly full of new good games)
3: Xbox (I can't imagine their line-up to be as dry in 2018 as is was this year, it's almost impossible even if they tried so last in the list but still 2018 should be better than 2017)