If a game can't hold my interest for 100+ hours then it's a problem with the game's design, not the game's length.
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When I play a Bethesda game, I know they've done something exceptionally well because I can actually enjoy one of their games for over 100 hours. Few other games do that special something that make me want to even play them for over 100 hours, but Bethesda does something just right with their content variety, in my opinion.
Largely based on whether the novelty of it has worn off. In some games, I got so sick of it, that 20 hours just felt too long to finish. In some rare cases, I get disappointed at the game coming to an end at its 100hrs.
I don't have a preference. Different games tell different stories, use different mechanisms, have a different need for attention. I would not want to play fifty hours of Call of Duty - that's why renting those games for a day is fine.