I voted Square because of FFVII and Chrono Trigger. Although the current Square worries me a bit. Hopefully they will redeem themselves with FFXIII, as I absolutely despised FFXII. Although I must say, FFX-2 is kind of a guilty pleasure for me. I absolutely loved it, more than any FF since VII. Haha, I'm sure I'm probably the only FF fan who would say that. But I loved how light hearted and fun the whole game was. And then the new game+ and multiple endings... Great game.
Although if you include SRPG in this mix, then I would have to say that my current favorite RPG developer is Nippon Ichi. I love the depth to their games. Loved Phantom Brave and Disgaea.