I don't hear a lot of disagreement on this one. Bayonetta, Xenoblade X, Yoshi's Yarn Thing, Kirby, Cap'n Toad, Smash Bros., new Zelda, new kind-of-Zelda, that squiddy thing that looks pretty cool - basically everything was a huge plus. Sony and Microsoft really dropped the ball on this one, and it seemed Nintendo took advantage of it all.
That said, I've been wrong before. If this is another case of fanboyism clouding my judgment, I'd like to know. Because otherwise, I'm just going to go ahead and say Nintendo won E3.