It's not easy to answer that poll. I'd personally go for a brand new Endless Ocean that makes good use of WiiU's graphics and Gamepad. I'd love that.
But since you're not giving me the option to go for it at the poll (shame on you ), let me see what's the second best option.
We already got a 2D Mario (two if you count Luigi) and, to be honest, that's enough for me. And we got a 3D Mario... but no matter how good it was, it wasn't the game we were expecting. A full scale 3D Mario would be nice.
F-Zero is one of those franchises that are always rumored but never make an appearance... until they do, to the joy of its fans. It could be ok, but it wouldn't be the big game we all want to see at E3.
A new Paper Mario game could be good, but it's a Hit or Miss kind of franchise. I prefer something else.
Pokemon games are kind of handheld only, and the 3DS already got X/Y and Ruby/Sapphire. I don't think a new one will be announced at this E3.
I'm not interested in Animal Crossing or Punch Out and Wii Music is simply a "Oh God, please NO!" game.
That leaves me with Metroid or a new IP. A new Metroid would be the big reveal of Nintendo's E3 (even if it's a 3DS game) and when it comes to new IPs and Nintendo, you can end with something like Pikmin or Splatoon but you can also en with something like the mentioned Wii Music or Giant Robot/Project Guard (yes, I know those were only prototypes, but they still left me cold).
With all what I've said, Metroid sould be my logical answer, but that's not how I apporach E3. I expect E3 to surprise me, to amuse me.
Because of that, I'm going to say a brand new IP ... and developed by Retro!
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.