Nintendo. Look at the WiiU's sales.

I would go with nintendo. They have been sticking with nintendo since the 80s (that is, the older fans of course). They buy nintendo games in droves and they stick with the wii u in spite of knowing that they will not be getting as many multiplat games. 

Sony

Da fuq

its a simple concept. Look at PS4 sales atm. Game wise there really wasn't much at launch that couldn't be bought on PS3 that would warrant an early adoption of PS4. Sony showed a shitload of future titles that will release and their fans believe that Sony will deliver on those.

Nintendo fans on the other had you see them type stuff like "I'll buy it when Zelda, Smash and MK come out" 

All fanbases have extremely loyal members, and all have less loyal members. I can't really say who has the "most" loyal, because there's "loyal" members for each.

Microsoft. The Wikipedia page on "brand loyalty" even mentions the PS4/Xbox One situation as an example:

"For example, if Joe has brand loyalty to Company A he will purchase Company A's products even if Company B's are cheaper and/or of a higher quality."

I say Nintendo, if only because they are more unique compared to MS/Sony.

Loads of Sony fans switched sides last gen, Nintendo fans stick to Nintendo, even if they buy other consoles on top.

I'm a Nintendo fan and I think Iwata needs to be fired

damn