The absolute platinum standard when it comes to platforming games. If SMB3 was a step forwards in comparison to SMB1, this one is a gigantic leap when it comes to level design, creativity, sound, difficulty and just overall player liberty.
My fear that nostalgia could be making my memories blurry when it came to how much I loved this one was just that, fear. Replaying this with an open mind and paying attention to what made this game work just made me remember why I stood in front of the tv day in day out playing this one.
It's not a particularly long game, the levels are very interesting and a bunch of them even have branching exits that lead to secrets or shortcuts. Naturally, I went for full completion so I did all the stages and did all possible exits for the ones that have that.
Difficulty wise, this one is a lot more forgiving in a good way. I may have finished the game with 99 Lives, but I lost quite a bunch on the Bowser levels and on the Special Stages (Tubular is still a pain in the butt lmao)
Overall, replaying this was pleasant, couldn't help but just keep a big smile on my face as I listened to the gorgeous soundtrack and saw the beautiful sprite work.

While I find SMB1 to be pretty good and Lost Levels/USA to be the standard messy sequel, SMB3 feels like the proper upgrade to the original SMB1 in everything possible.
More upgrades for Mario, tighter level design, one of the most beautiful soundtracks for a game of this time, a bunch of minigames and a ton of freedom for the player to do whatever they want to do.
Maybe my only grasp with this one is the obscene amount of scrollers in this bad boy.... doesn't help that every final stage in the world is pretty much one, too.
The difficulty in some spots can be borderline trial and error, too. Which is fine, the game hands you extra lives like a madman, but I'm not too fond of it. Possibly these two things are what push this game a bit back for me at least.
Still, this game was my absolute childhood, alongside SMW! It's definitely a gold standard when it comes to difficult platform games.