I think it's probably Nintendo. Although obviously all 3 have their die hards.
IMO it's because Nintendo for many of us evokes childhood memories (the N64 was what properly introduced me to gaming and Mario Kart 64, Goldeneye and Banjo Kazooie defined several years of my life. even though I'd had a Game Boy and Mega Drive beforehand). And they also make games that you can't play elsewhere.
And I don't mean in terms of IPs, obviously Kill Zone is only on Sony and Halo on Microsoft, but both are in essence Generic Brown Space Shooter. Pikmin is only on Nintendo, and there are no similar games. Mario Kart is only on Nintendo and there are no similar games (quality wise). And so on.
These 2 points, IMO, are what lead to Nintendo having fantastically loyal fans.
Even though I sold my Wii halfway through last gen as it wasn't getting used, I still queued up for the Wii U day 1. Because after 3/4 years of gaming almost exclusively on 360, I missed that Nintendo feel. And I am in no rush to get another console. If certain companies would release certain games on the Wii U I wouldn't get another console.







