I first played Cave Story (freeware) in 2011 or 2012 and at the time I didn't even know there was a better ending than the normal one. I figured that Kazuma wanted to give me a bad one. It's quite logical if you think about it (you don't just play the entire game to fly away safely like a coward). It took me far too long to get past the Misery-Doctor-Undead Core boss combo, but once I jumped off the island with Sue like an idiot, I found seeing Curly in the core room very depressing. I remember being like... "dude, why would you do that... that's dark, jeez." But even then, I was pretty certain there wasn't a better ending because I couldn't find any way to save Curly. Little did I know I just had to ignore Booster and I had very bad internet back then so I didn't look it up.
But yeah, it wasn't until recently that I bought the Steam version and played it again. One of my best friends made a Cave Story song a few years ago that I liked and kept listening to for a while, which is what motivated me to try the Plus version. This time though, I did know what I had to do to get the best ending.
It took me days to beat hell. At a certain point, I even felt like giving up. But I have watched some playthroughs on YouTube which helped me learn some strategies.
The day I beat hell for the first time was one of the best days of my life.