1. Best Zelda games for start are Ocarina of Time 3D or Zelda Wind Waker HD.

2.

3. Maybe "That effing thing seems so awful" but it pretty comfortable and have good use in Zelda Wind Waker HD.

4. Depends of your play style, I beat last 3 Zelda game that I played in around 40 hours, Twihilight Princess, Skward Sword and Wind Waker HD, I hope that will for Zelda U need at least 50 hours. :)

A link to the past is a good entry point, and is the most easy to get via virtual console. Ocarina of time is good too, but is kind hard to find, since there is no more reprints, but its still on the eshop. These 2 are probably the only universal acllaimed games in the series, all other have a big amount of critcism. Even ocarina get some, but not near as big as the others.

Another things to consider: 2D zelda games are hard. You will get lost pretty easily and some bosses really kick your ass. 3D zeldas are easier in combat and in puzzles, but have some handholding.

Most of the 2D games are shorter, specially the portables ones, but some of them doesn't involve zelda at all.

Almost every zelda game can be played independentily, since their history is not linked. But not all of them. The following games have some correlation between then, so consider that before chosing one.

Zelda 2 is a direct sequel to zelda 1.

Majora mask is a direct sequel to ocarina of time.

A link between worlds is a sequel to a link to the past

Phatom hourglass is a direct sequel to Wind waker

Oracle of ages and oracle of season can unlock content one from the other.

The minish cap, Four swords and four sword adventure are linked in some ways, but nothing too big.

1. Each Zelda game stands on its own (except Majora's Mask). Prior experience with or knowledge of Zelda is not required to enjoy any game in the series (except Majora's Mask).

2. The Wii U has access to 9 out of the 17 main entries in the series: Legend of Zelda (NES), Zelda II (NES), Link to the Past (SNES), Ocarina of Time (N64), Majora's Mask (N64), Wind Waker HD (GameCube / Wii U), Minish Cap (GBA), Twilight Princess (Wii), Skyward Sword (Wii). Yes, it is backward compatible with Wii games.

3. The Wii U has many controllers, though your options vary by game. Zelda Wii U will most likely support the Pro Controller as well as the GamePad. But it's not as bad as it looks.

4. 3D games in the series do indeed typically take over 30 hours to complete. If you want something shorter, 2D games (Link to the Past, Minish Cap) fall more into a 10-15 hour range.

1. There are barely any offshoot Zelda games. Think of it like Power Rangers where each season completely changes the plot and characters, but there are certain things you can expect to see in any season. You will understand the new one without playing any previous zelda.
2. The Wii U is backwards compatible with the Wii. You can get every 3D Zelda game (5 so far) on the Wii U because some of these are on the Wii virtual console. Specifically: Windwaker has a HD remake on Wii U, Skyward Sword and Twilight Princess can be gotten on Wii and Ocarina of Time and Skyward Sword can be gotten on Wii virtual console.
3. The game is being built from the ground up for the wii u gamepad. They might throw in a pro controller option, but trust me, if you actually use the gamepad for a few hours, you'll wonder what you were worried about in the first place.
4. 15-30 hours probably refers to the top down Zelda games that appear on handhelds and pre-N64 consoles. The 3D zeldas are usually in the 50 hour range, which is one of the reasons the games get so hyped. Those 50 hours are usually packed with lots of awesome stuff and little filler.

As a Zelda fan, I'd say you should aim to play almost the entire series. There's no deadline because you don't have to play them before the new one comes out. But if you insist on beating them before playing the new one, at least beat Ocarina of Time. Every other 3D Zelda is unique in a way that makes certain titles more loved or hated amongst Zelda fans because each of us loves a different aspect of the series the most. For example, I would say Skyward Sword is the best Zelda so far and you should totally beat it, while someone else would say Skyward Sword is one of the worst for the exact same reasons that I love the game.

1. A Link to the Past, playable on Wii U.  I'd say Ocarina or Twilight Princess but they're both long as hell.  Every other game is passable.

2. Yes and yes.

3. Probably the classic controler or the Wii U pro controler.

4. Yes some of the games are very long.  Wind Waker and Skyward Sword in particular for their unbareable amount of filler.

The original is very lengthy because of challenge; Zelda II is one of the hardest games ever, don't bother; Majora's Mask is a weird, almost spin-off kind of Zelda.  In many ways it doesn't even feel like Zelda but it's not bad either. 

Get a Wii U, you can then play Zelda U and Windwaker HD, and also have access to the NES,SNES,GBA and soon to be DS Zelda games. If that isnt awesome enough, you can also get to play Skyward Sword and Twilight Princess via backward compatibility. After you are familiarized with the Zelda universe, check out Hyrule Warriors, i know its a crossover, but its a fine game.

Wii U is backwards compatible, you could play the WWHD, download the first few on the virtual console, get Hyrule Warriors, and look forward to Zelda U

The Wii U Gamepad it´s the best controller ever created, so don´t worry if it looks "awful", you will love it.

With this comment in mind,some are pretty big but they don't really take that long to beat, you can finish Ocarina of Time around 10 hours easily, I finished the 3ds version in 7:30 hours which is also regarded by many as the best Zelda game ever, though I highly recomend Skyward Sword which is rather longer -maybe around 20 hours for the avarage gamer- I woudn't recommend you try any of the 2D Zelda really, I mean they are nothing like what you saw in the Zelda U trailer, and if you didn't feel attracted to them before you might not like them, thought they are also very fun, simple and rather short, they feel much like the best inde game you can think of, (if you like indies then yeah definetly try them). This comes from an honest guy that's played every Zelda game ever.