I have 30 years of unfinished game backlog.
since I'm 10, I tried lot of games, either I bought, pirated (long ago I used to, not even counting emulators!), or were lent to me from a friend and I had to give back before completing.
Like Tom Bombadildo, I could write a full book
And there are so much I still want to "try", even just the beginning, not necessarily "complete", just to know more games and make my own idea of all existing games. Sometime I see people talking about a game or a sequel, and I wish I knew the game too.
I tried to list the games I remember ever playing on backloggery.com, and I currently have more than 500 games I didn't complete (but 227 completed!). not counting the one I forgot, such as a lot of amiga games or from weird machines I didn't even know the name and still wish to remember or try again.
edit: not counting homebrew I tried either
Though, I have a tendency of playing games up to the end, but never completing them
FF8 (last boss, I skipped all other battles since the beginning... because it was an option... haha, I can't beat last boss without Lv or Exp)
Zelda Wind waker (last boss not even tried, I want to complete and find everything...and lost interest))
Zelda Breath of the Wild (last boss not even tried, I want to complete and find everything... I did all the quests, then bought DLC and lost interest)
Star Ocean 2 (last dungeon, I had other games to play and forgot about that one)
Star Ocean 3 (last dungeon, difficulty rocketed and is impossible to advance in the story without dying in one hit)
All castlevania game before SotN, because of game's difficulty
etc.
that's just few examples, I have tens like that.
Sometime it's only because of game difficulty (old games you had numbered lives, or continues) and often lost all lives/continues on last level... so frustrating! (shoot'em up, plateformer, etc.)
of course there are also a lot I just lost interest, or didn't had time because games I want are released too fast. or either I'm too slow to play. (death stranding: I'm still chapter 3 after 6 month and 80H, when some people completed the story in 30H...)