Because the Wii U was still a thing only 2 years ago, and the Switch isn't that different from the Wii U specs wise, Nintendo sells almost the same games as it did with the Wii U and still one is a huge failure and the other a huge success. And all happened in less than 2 years. There is still people over there who don't believe in the success of the Switch or minimise it. But it's really a blockbuster success.

It is more impressive for the Switch to sell way way more than it predecessor (it's like day and night) than the PS4 selling like most of PS consoles before it.

I'm trying to give you an inch but you're taking a mile. 

I agree with you, it's just also understandable why some people think the PS4's sales are also impressive. Most weeks that kind of attitude annoys me as well, but here it's kind of understandable. The PS4 is just a beast of longevity. 

I think the battle is more so lifetime than it is week by week anyways, what will be more interesting is how much sales Switch can keep in year 4-6. 

The Switch isn't the successor to the 3DS, it is sold at the same time, while the Wii U is discontinued. New games are coming for the 3DS. And the Switch is sold at the same price as the Wii U and have the same library as the Wii U, not the 3DS. That's why it makes sense.

And for your comparison Wii U/Switch vs PS3/PS4, you must be joking. The PS4 didn't outsold the PS3 in 1 year, and didn't sold twice as many in less than 2 years. It actually got 5 years to the PS4 to outsell the PS3, close to the end of the generation. So that comparison makes no sense at all.

Every generation, before new home consoles are coming, some people say that gaming is moving towards mobile, and home Consoles will be in serious trouble. Some people have said that before PS4 came out, and guess what, PS4 will easy pass 125M units sold by the end of its life cycle, and this is my very conservative estimate.

 Sony and MS will never release a Hybrid piece of Hardware, 'cause they want to give us a true Next Gen experience, with mindblowing graphics, physics, more complex and life-like animations and advanced AI.   All the best/most impressive 3rd Party AAA titles will only run on PS5 and Next XBox, and if you wanna play them on Consoles, you need to buy them, not a Switch, or a revision of Switch, which will be so underpowered in comparison that nothing will be able to run on it, unless you "reinvent" the game to such an extent that it would be virtually unrecognizable on the Nintendo console, and no Pubisher/Developer on Earth would do it.  It's all about Sony and MS; if they release something great, they will have success; look at XBox360, look at PS4;  Nintendo has nothing to do with it, Switch cannot affect the future of Sony and MS; Nintendo is offering its own game experience, with a hybrid hardware, hybrid generation, they are selling a Home console and a portable console together, this is why selling numbers are good. PS4, which has entered its 6th year, is still doing better than Switch(2018), a very old Home Console is till doing better, all in all, than a new Hardware which combine Home console and a Portable, can you imagine ? And you say :" Sony can still survive Next Gen..." are you kidding or what ? :)   After an absolute domination of ps4 for over 5 years, you are questioning the future of Sony ?? And based on what?  Your hopes and assumptions ? Videogames Hystory has teached that what you say makes no sense at all.

But Wii U was a disgrace and PS3 was quite successful.

We can't compare Wii U with PS3. Wii U was abandoned and was a huge failure.

NSW has Wii U library but it also has 3DS library. Wii U didn't have Pokemon.

Switch is the successor to 3DS and Wii U. That being said it can compared to whatever you want. Its very successful so really that's all that matters. To have a 3.61 Software Tie ratio in its second year is pretty amazing. And 2019 is where it should really heat up. That doesn't take anything away from the success of PS4. The most interesting thing is 2020 and the next generation and what the transition will be, and what will be offered. I am greatly looking forward to it.

No you can't. You can't compare a NSW to a rock.