You don't really need five polls to accomplish this. Lets just look at sales charts.
PS4: 2 out of the top 20 games are exclusives. We can logically reach the conclusion that most people buy the PS4 to play multiplats.
Xbone: 4 of the top 20 games are exclusives. We can logically reach the conclusion that most people buy the Xbone to play multiplats.
Wii U: 19 of the top 20 games are exclusives. The only exception is ZombiU, which recently went MP. We can logically reach the conclusion that most people buy the Wii U for exclusives.
That was easy. And way more credible for your research than forum polls.