The killer VR app, for the next few years at least, is going to be porn and other video. A $200 dollar phone will be able to pull this off with ease. Google has realized this and the next gen of VR capable android phones should provide a more than adequate experience.. Casual games should also be no problem. A fully realized, computer rendered VR experience that does not make one sick is still a ways off as a far as I can tell.
I for one am more interested in AR and am waiting to sea what Magic Leap ships. I think that high-end, complete isolation systems will mostly be relegated to amusement parks and theaters. They are impractical and even dangerous (think parents with toddlers...) for frequent home use.