My two:
Very cliché, I played Ocarina of Time a ton as a child, have memories of playing it both on N64 as a wee child and on game cube as a less small child. Never got past water temple even with the game guide.
Yu-Gi-Oh forbidden memories. Played the crap out of that game on play station, constantly playing on free play praying for the cards I would need to get further. I was never able to beat more than 1-2 of the high mages. Watching speed runs on the game it turns out I was never ever going to beat that game as a kid. The final 6 are just disgustingly brutal.
None. If I enjoyed a game enough to play it a ton, I will eventually beat it. And not just beat it, but get 100% and all the achievements when possible.
The only games I played a ton but didn’t beat are open world games that don’t have a set objectives.
That’s one way to tell us that you’re probably not old enough to have played a good number of original NES games without emulator save states. People like to say that Soulslike games are hard, but some of those games were absurdly difficult.
I mostly played Zelda, various mario bros games and adjacent stuff. But there was a serious time investment into getting 100% runs on many of those.