1. Incredible dungeon design. Level design that blows Super Mario Galaxy 2 and Portal 2 out of the water. No, seriously. The dungeons are a big focal point of every game, and, in my opinion, would make or break the ultimate Zelda game.
2. Perfect graphics. HD graphics, to be more specific. I know some fans would cringe, but that Wii U demo made my eyes water with excitement! Just imagine what the future of Zelda could hold thanks to the power of the Wii U!
3. Terrific story. The plot is central to an ultimate Zelda game. I like the idea that another user said about bringing back past friends and foes, and this would certainly be awesome, but I want Nintendo to be as creative as possible, and unleash the big guns when it comes to plot.
4. Side quests. Side quests, side quests, side quests. I can't stress the importance of side quests enough in Zelda. One look at Majora's Mask shows that it's chock-full of side quests, and the ultimate Zelda game could learn a thing or two from MM, and really extend its replay value.
5. FULLY orchestrated soundtrack. Emphasis on the word "fully". Nintendo never really commits when it comes to a "fully" orchestrated soundtrack. The ultimate Zelda game can redress that, and imagine what sounds can be produced in this game!
6. Last, but not least...........voice acting. Voice acting would really spread this apart from previous games, and it can be considered "ultimate" once it fixes this one problem.
Geez...now I'm all excited!!