When I was really young, first starting out in games, I would just play the first level of games. Not just once and then move on; I'd play the first level over and over again. I found it fun just playing the games and discovering more of it wasn't something that interested me and increasing the challenge would've put me off even more. Donkey Kong Country 2, Wario Land, F-Zero, Tony Hawk. Even stuff like Myth: The Fallen Lords and Populous: The Beginning. The first game I actually remember finishing is Barbie Super Sports.
As I grew older, I always had enough access to new games that I was never spending enough time with any one of them to complete it. There were a few favorites I would finish, but this is really when I found the pace of spending an hour or two with a game before moving onto the next one. I would usually stop whenever I got stuck on a boss or a puzzle. It's not that the games were too difficult, I just lacked the motivation to push through and beat the thing.
Nowadays, the hand-holdiness of mainstream games allows me to get through most of the big triple-A releases I play without too much difficulty. Sometimes I even go back and finish some I never got around to when they were first released. Smaller/indie titles are completed based on length and difficulty and I usually don't spend more than a couple of hours with a game before I pick up the next and never look back. That Last Livestream Of The Year taught me that I have more Steam games than Jeff, so can you blame me if I don't do a deep dive on all of them?