I like Nintendo because they were the console I owned when I was a child and their games were fun. They were everything I thought video games should be at the time. If you had a Nintendo console in the Nes/Gameboy/Super Nes era, you didn't need anything else. You had all of the great games and the few you didn't have didn't matter. I'm hoping for a return to form.
I semi-dislike Sony because it seems like they didn't earn their spot in the gaming world. It's like they beat the champ because the champ slipped on a banana peal or something. Though I enjoy their consoles (owned every single one of them--even the portables!), part of me enjoys seeing them screw up.
In my mind, Nintendo got where they were because they were creative, innovative, and produced really incredible games. Sony got where they were because third parties gave them great support. Only now, after 10 years on the market, is Sony actually trying to make the best games on their console.....and even then, very few of their franchises are what I would consider "must play" (and those franchises are Uncharted--though I'm getting fed up with Nathan Drake's personality--Heavy Rain, and God of War. Heavy Rain isn't even made by Sony. I was a fan of Quantic Dream with Indigo Prophecy last gen. The rest are pretty "meh".
I'm not really a fan of Microsoft, either. The 360 is just my third party system of choice, now. In this day and age, third parties are the bigger deal. Nothing from Microsoft/Sony are what I would consider generation defining experiences. Not Halo. Not Uncharted. Of the "big three", only Nintendo is creating the must play games, in my opinion. The other two just rely on graphics and horsepower. If Nintendo had great third party support and a more powerful console (I was a bit let down by the Wii), I probably wouldn't have had a need for the PS3 and 360.
And there you have it.