Well, in a perfect world you'd own everything. I've played great games this gen on WiiU, PS4, XOne, 3DS, PSV, and PC.
But if you could only limit yourself to two ecosystems, Nintendo and PC is by far the best combo -- assuming you own a capable rig. Nintendo has, by a wide margin, the best exclusives on the market, and PC supports most of the third-party content available on PS/Xbox, in addition to its own exclusive titles. By comparison, the first-party exclusives on Xbox and PS4 are rather pedestrian. Now, PS4 does host some Japanese titles that can't be found elsewhere, e.g., Bloodborne, Nioh, and Nier Automata. Those make the Sony ecosystem more attractive than the Xbox ecosystem, but both still trail behind Nintendo and PC.