I cannot wait more than 3 years between each game. How would I survive 6 years? I can't, simply can't...

There will always be handheld titles in the middle. Also you should buy Tri Force Heroes if you havent, its sooooo much fun. 

One thing u seem to be ignoring is that the Zelda team makes multiple other games between 3D Zelda titles while up until recently Naughty Dog just worked on one game at a time.

Between Twilight Princess & Skyward Sword, they also released Link's Crossbow Training, Phantom Hourglass, Spirit Tracks and between Skyward Sword & Zelda U they released Wind Wake HD, Link Between Worlds, Triforce Heroes.

I think the main problem is Aunoma has too much on his plate juggling between 3D Zelda, 2D Zelda, remakes, spinoffs. They need a second person to be in charge of a separate team where they can split the load. The 2D & 3D Mario games are developed by 2 separate teams and so should Zelda.

If Aunoma was working strickly on 3D Zelda, I think it could feasibly be released every 3-4 years instead of every 5.

No, just finding completely new, unique, great and beautiful art style and graphics alone, or just finding dont finding new mehanics, or just beacuse is first HD title, dont justify 5 years development. But finding completely new, unique, great and beautiful art style and graphics, and finding and implementing completely new mechanics and staffs, and developing very complex dungeons and epic bosses, all that for open world adventure game with NPCs that is developed by team which in same time working on other projects too, and we add to that Nintendo obsesion of releasing very polished games with no bugs or any problems, so all that together clearly justify 5 years of development. If we talking about Zelda U, will add to all that that is first HD, true open Zelda with bigest world by far than in any previous Zelda games.

Finding completely new, unique, great and beautiful art style and graphics for every new game is definitely much harder than go every time for realistic graphics, especially when today almost every AAA game looks same.

So no Zelda team isn't inefficient at all, all things they are doing requires time and definitely justify 5 years of development. 

Also you cant compare at all development of games like Uncharted or Killzone with development of 3D Zelda because of all of staffs that I mentioned. Also Zelda series is unique and very different series than any other series on market, you can't say same for Uncharted, Killzone or even Skyrim, and that certanly also is afecting on devolpment of 3D Zelda games.

But because with NX we have unified platform, and Zelda team already worked on HD and true open Zelda with huge world, I think we can expect completely new Zelda for NX around 4 years after Zelda U, but if they decide to pull again MM, probably for 2-3 years.

Don't worry. If Zelda X releases in 2021 and Zelda Z releases in 2027, it must mean that Zelda Y releases in 2024. Also between Zelda U and Zelda X there will be Zelda V and Zelda W. Should be a steady stream of Zeldas.

I would say this is true, except I do think they're really re-inventing the wheel this time around in a way not done since OoT. If it pays off like I suspect it will, then I can see them using the foundations of Zelda U for a quick 2-3 year turnaround of another Zelda title, with maybe a more niche and experimental tone. So in other words, exactly what they did with OoT to MM.

Yeah. 5 Years is a good cycle.

There is nothing uniquely demanding about developing cartoon action adventure games, or coming up with new art styles, or designing dungeons and bosses. (neither of which have really gotten drastically more complex since Ocarina of Time on the N64)

First HD game and open world are the only things you mentioned that are actually demanding, and even then we've seen other companies like Bethesda and Rockstar pull both off in 4 years.

Like already wrote, all things comibined that I mentioned clearly justify 5 years of development.

No, they don't. Other developers have proven you can make your first HD open world game in 4 years. For a competent and efficient developer, art style/etc would not add another whole year.