The clear winner for me is Fallout 4. I said it in the main E3 thread, and I'll say it again here; That was probably the best E3 stage demo I've ever seen. It went off without a hitch. They showed a lot. What the they showed looked fantastic. They released a free game right in the middle of it. And it's coming this year. You can't beat that.
My first runner up is Just Cause 3. For no other reason than it out of all the games I saw at E3, this one looked the most FUN. Just Cause 3 is a big, dumb, explosive, insane action game. It knows damn well what it is and it revels in it.
My second runner up is Horizon. I was skeptical when the whole "robot dinosaur" concept leaked. However, seeing it in action really sold me on it. It's a fresh IP with a cool concept and world, and it looks pretty fun to boot.
I'm also going to post some honorable mentions I guess. The first of which is Super Mario Maker. This was going to make it in my runners up because I think it looks amazing. However, I always get hyped for games with level creators because my mind is instantly filled with like a hundred great ideas, but I always suck at actually making them and get frustrated with the game as a result. It's not fair to hold that against one of those that I haven't tried yet, but just know it's going to happen.
My other honorable mentions are Doom 4 and Ghost Recon: Wildlands.
Doom 4, like Just Cause 3 above, knows precisely what game its trying to be and doesn't shy away from it. It also happens to be significantly closer to what I always wanted out of a modern Doom game than Doom 3, which I found to be pretty disappointing.
Ghost Recon: Wildlands apparently has this game structure that I love and that very few games have. Basically it's like Crackdown or Mercenaries, where you've got this kill list, and then they just let you loose in the world to take them out however you see fit. I imagine it's going to be a great game to play co-op with my buddy as well.