Updated with my reasons

Nintendo. Their games and their policy.

Sony playstation - Constant supply of new IPs, Anime games and brand loyalty.

nintendo or microsoft hmmm.....
i really like microsofts ips and hardware and online infastucture
while i love nintendos games free online and cheapness
im gonna have to go with nintendo its peaceful in miiverse more than xbox live

I like Sony because it has the exclusives I like and they give me 5 free games every month.

I like Nintendo because they have all the Nintendo games.

Nintendo - They make my favorite games. They make quality hardware. Their gaming devices are superb at what they do with the software that is in mind.

Sony - They make great entertainment devices with many features for a decent price. They've learned to be more modest and malleable by consumers than the other two.

Microsoft - Don't really like them too much these days, but historically they helped by competing with Sony and by pushing boundaries, such as online gaming.

Sony because of the variety of games that aren't seen on the other two consoles.

MS, they give good head.

It has always seemed to me that people's company of choice aligns heavily with what ever console they like the most in their teen years to early twenties. The time people are forming their own identity in the world. Psychologically speaking it is the time this happening for people.

Sony because of excellent hardware, diverse 1rst party stable with a constant stream of new ips in between. Add to that that i dont trust microsoft and think their live gold is a ripoff (although improving) and nintendo doesnt habe much interesting imo. 3rd parties are also nonexisting on it +they have the worst hardware. I will say though that i also game a lot on pc but mainly strategy titles like hearts of iron or company of heroes