First impressions are important; the first level in a game needs to introduce its core framework in an engaging way and hook the player so they stick with it.

What do you consider the best opening levels in gaming, and why?

(If the opening area of BotW counts as an “opening level,” then that def wins IMO. Otherwise…) Super Mario 64 seems like an easy winner. Super Mario Odyssey’s Cap Kingdom was also really cool.

Kingdom Hearts 1 hands down (the whole Dive to the Heart sequence). Not only teaches you how the basics of the gameplay work in a very engaging way, but it also sets up the story beautifully by giving you the right amount of mystery and by making you take some personal choices.

It really makes you want to keep playing, not just because it's fun, but because you want to know what is going on and what is going to happen.

City Escape in Sonic Adventure 2.

The overall hype of the opening scene, the music and the level design.

MGS2 Sons of Liberty. The opening in the rain and the first mission, especially with the sound design were sublime. Instantly hooked.

Most Ratchet and Clank Games have great first levels. I think Tools of Destruction and Rift Apart (first experiencing the rifts) are the most epic and memorable.

The playable prologue for The Last of Us is an emotional gut punch.

Taking down the first Colossus in Shadow of the Colossus.

Shining is the best track and skin in Lumines and its the very first one.

The original God of War from 2005 has an amazing opening level. So do GOW III and GOW 2018.

Darksiders 2 have a amazing first impression, mainly in the first level.

Bloodborne

The horror of not being able to level up where I desperately try to survive all the horrors and enemies in Central Yharnam really left an impression on me

It's pretty overwhelming. You have few HP, not many healing items, there is an ominous presence surrounding the city, people are inside their homes and won't be out (you can talk to them and see they are all frightned). It's equally atmospheric and HARD

And of course the level design is just suberb as always, with many secret locations and shortcuts, it took me a while to find them all 

MGS will always be my favourite from boot and the Konami jingle to the elevator sequences, snake taking off his gear on the way up with the title card but Doom 2016 was the fastest a game hooked me. It was such a refreshing at the time and made the statement that this is going to be a no nonsense game just killing Demons.

Nier Automata, the entire intro sequence up to the point where you fight the 2 Engels bosses is fantastic.
Bloodborne opening area is goated.
BOTW's great plateau is quite nice
Megaman X's opening scenario is memorable
The opening of Spiderman (2018) is quite good as well
God of War 3's intro with Poseidon is goated

Honestly? Elden Ring's begining areas are great as well, right after you fight Soldier of God, Rick you get called maidenless by a random, and a big dude on a horse murders you. Priceless.