Microsoft NEEDs to have a good one (with a roadmap, showing whats happending in 2019,2020).
Nintendo COULD use a good E3, but people know Pokemon, Metroid, Smash, FireEmblem ect will come somepoint.
Sony Basically dont need to do anything at E3 and it ll still have a great year.
Microsoft > Nintendo > Sony (in terms of dependancy of this E3)