I haven't made a final decision as to what my favorite game at E3 2012 is yet, but Epic Mickey: Power of Illusion for the 3DS is right up there.
When DreamRift's game was announced a couple of months ago, I was shocked. Instead of just being a straight port of the 3D Epic Mickey sequels on other consoles, Epic Mickey: Power of Illusion is a brand-new 2D platformer releasing for the 3DS.
And just look at the game. It is beautiful. If you are a fan of any of the old Capcom Disney games for the Super Nintendo, you are going to lose your mind over this.