This was a huge suprise. I know there were leaks, but new 2D Metroid has been a "pie in the sky" for so long I still did not expect it.

19 years!

19 YEARS!

I found the graphics to be ok. It's not that I'm expecting high quality assets, but maybe a more artistic and stylish design for enemies and background alike. I won't prevent me from buying though 

I hope it's more exploration-heavy, but I'm feeling this game will be pretty linear for the sake of accessibility -sad

It's not. Side strollers doesn't have the same perceiving value of 3D games. Pokemon and Mario sells based on their branding mostly, when you get that you are buying to yourself a luxury product almost. Plus they are know mostly for their 2D games, it's like 2D is part of identity of both franchises so consumers feel ok paying them because it's just how the things are

Minor franchises and new entries does not enjoy such status, a 60 USD price will for sure affect potential here. 

The most exciting E3 game announced so far.

The feeling is mutual.

The original Metroid has a certain charm. It's the most open game in the entire franchise, allowing you go to anywhere you want and skip almost every power up. However, it's an absolute nightmare to play unless you are really into old clunky games. No diagonal or down aiming, no crouching, enemies can hit you even if you are going through a door, password saving, tons of clonic rooms with no other purpouse than to confuse you, no map, no way to refill your HP and ammo other than the painfully slow method of killing infinite enemies that come off pipes...

Honestly, I cannot comprehend how someone could say that METROID (NES) is better than Super Metroid. Other than being an interesting experience for a fan of the series that started the franchise with newer games or a nostalgia trip for those who played it on its time... it's not a very good game at all. Even by NES standards.

BTW... light spoilers from Metroid Fusion:

I am having the same concerns as you. Metroid didn't sell well even on popular devices such as DS and Wii. We can argue about the fact that switch is the system that managed to get together casual and hardcore gamers, so the game won't have the same issues with the fanbase as Prime3 did on the Wii or Hunters on the DS.
However, there's a double edged weapon over there which is the attraction towards Metroidvanias' that was generated by Hollow Knight. We might think that there's a BIG new consumer installbase of new comers to the genre to welcome Metroid DREAD. But THERE is where the problem lies. Hollow knight has become THE reference when talking about metroidvanias nowadays. It revived the genre and the most important thing about it all, is that it has a price tag nearing the 15€.

People will compare Dread to hollow knight and Ori no matter what, they'll see both more appealing, challenging and more importantly,CHEAPER than Dread, and then will refrain from buying it.
I am already sure that the sales won't be high just for those arguments that I listed.
Major buyers will be old fans of the series and it will be expected to hit the 2 Millions as a maximum.

In the other hand, i have no fears for Metroid Prime 4 to sell extremely well.There's hype behind it, people ask and love shooters, people love 3D games with vast environment. Hitting the old Zelda's milestone of 7Million copies will depend on how good the game will look.

The main thing for me is the exploration.

I like the "no mini map" either memorize or draw one for your self. The maze like structure of the game means you come to a dead end and need to turn back and find another way. All promoting the exploration feeling of the game. 

The aiming thing or no crouching thing hasn't bothered me since the game is designed not to have it anyway. It's just a mechanic you learn to cope with.

Nothing with this feels clunky to me. Want to talk about clunky feeling games, play the NES Castlevania where once you hit jump you can do nothing to change your trajectory. Or Dark Souls where the clunky controls are hailed as the second coming of Christ because "you have to know the button press dedicates 2 seconds of time to the coming animation and you can do nothing to change it". 

Only thing I really agree on is the password system and having battery backup in the NES cartridge would have been nice. But back then in most cases it was either passwords or no way to save progress anyway. 

Last time I played through it was a year or two ago on the Switch. Given I still remember where to go so I finish the game way faster than my first time playing it. During this play through I use the save state function instead of passwords.

To me this is one of those games that I wish I could experience for the first time again just to get that feeling of exploration that is lost after the first play through.   

But as with everything YMMV, this is all my subjective opinion.