These come to mind...
Fire Emblem: Three HousesFinished Edelgards' campaign so technically finished it but there's 3 more paths that I haven't
Fire Emblem: WarriorsDipped my toe into this, didn't return when Houses came out
C&C RemasteredPlayed nearly all of C&C except for the Dino missions. Wanted to start Red Alert but never did
Zelda: BOTW (2nd playthrough)Originally played this on Wii U without the DLC, I've now gotten up to the second Master Sword challenge, 1 Divine beast to go and about 30 shrines.
Trials of ManaAt some point I got stuck at a boss and didn't return.
Super Mario Maker 2Never finished the story mode
Forza 7 / FH4As with all Forza games, I just drop them
Assassins Creed: OriginsStarted this after odyssey, great game but a time sink, played RE3 first then didn't return
Ace Combat 7Got pretty far but the difficulty ramps up, dropped it after a while, it'll be difficult to pick up again so that's what's keeping me
CONTROLNearly finished this one I think but my PC started acting up. Easily one of my favorite games of the past year too. Now that I have upgraded my PC I can finish it, some day.
Half-Life AlyxThis is awesome but again because of PC troubles I dropped it. Have to return to this at some point.
Xenoblade Chronicles 2One of those games I play for a while and then drop again. I should be pretty far along but who can tell in these type of games.
CelesteDifficulty kept ramping up and I like my platformers not too difficult.
Once I've completed Cyberpunk I'll probably return to one or more of these starting with Half Life and CONTROL.
And this doesn't count the games that I bought or I got as gifts and I never started like Red Dead Redemption 2, Batman Arkham Knight, Xenoblade and Star Wars Squadrons.
Because I play most games once, my playthroughs are usually close to 'completionist' on the first run. Which just takes longer and also means I might abandon a game because I get burned out on the side content.
It is also not how most games are designed these days, they seem to cater towards quickly rushing through the story and then doing New Game+ to mop up the rest.