As someone who has a PC, Wii U, and PS4, I must say that until today the only thing I really felt I NEEDED to own was the PC and Wii U, as almost every major title I have on the PS4 was also on the PC. After this E3 it finally feels like the PS4 is also a necessity.
Xbox1 isn't there for me... I just feel no need to get one, and just about every time they reveal a new game it's also on the PC.