A mark of a great game is its replayability. I know for some that's difficult because of the knowledge you have afterwards, but it can still be fun to relive things. On the flip side, a not so great game is the one where you never want to go through the struggle and grind again because it frankly wasn't fun.
Some games are challenges that many people feel as completed when they finish it. For me, that would be Portal. The storytelling through the setting was great, but the main focus was the puzzles which aren't as fun the second time through. Portal 2 has a great story that makes it fun to replay, but that doesn't mean Portal was a bad game because it didn't have a story line worth replaying. Plus Portal 2 had the additional custom puzzles that made it worth playing outside of the story itself.
Being an unfun challenge is definitely the sign of a bad game., or at least a bad match for the player. I'm sure there are plenty of people who think Dark Souls/Elden Rings are bad games because of the frustration factor, some only play it once to get the satisfaction of beating it, and there are people who play through it over and over again.
I see myself in that Elden Ring part. I went 100% to prove a point, but was very bored of it for most of my playthrough. I completely understand the appeal, but the gameplay loop doesn't click with me. Every person is different and fun works just as differently for everyone.
I see my addiction to TBS games and can replay them over and over again, no matter how repetitive and have my wife literally fall asleep while playing with me.
I strongly agree with this. There are so many games out there that if you asked someone if they were excited to replay it, they just be confused. Like, what's the point of playing a game that's mostly going from cutscene to cutscene?