This is my exact issue. A lot of games I play are quite open ended, or have lots of replay value to them. For example, I'm a big fan of Bethesda games but I don't think I've ever finished the main quest in ANY of them. Fallout 3, 4 and New Vegas, all the Elder Scrolls games... never "beat" any of them, but I have a good 600 hours if not more across all of them. Then I play games that are so large with so much stuff to do in them that I get bored before I can finish them. As much as I love the series, I have that issue with a lot of Yakuza games.
I think I'm spoiled for choice. I have so many games and if I took the time, I could find 100+ games I'd like to eventually get around to playing. My issue is the fact that there are too many games, and I get too enticed by newer games too. It's a problem I wish I didn't have, but at the same time I'm not doing anything to fix it. I really should make a backlog and try my hardest to go through it. I don't even know where to begin though.. replay an old favorite or start with something I haven't played before? According to SteamDB I have over 600 games I've never even started up.