If you're looking for something that isn't one of those massive triple-A games that take up 80+ gigs, that's where the problem is because almost all decent PS5 games take up a ton of space. That said, there are some that compress pretty well without sacrificing graphics. Ghostwire Tokyo for example looks incredible but isn't as heavy as others, and if you're into the supernatural-mystery genre, it's addictive. Another option is diving into polished indie games; there are titles that came out a while back but are still visual masterpieces.
What works best is thinking about what specific genre really appeals to you. If you're into fast action like hack and slash, there are some pretty well-optimized options. If you prefer something slower or story-driven, graphic adventure games take up less space. And if you're patient, remastered PS4 games that got improved for PS5 are a solid bet because you already know if you'll like them or not.
One tip: before downloading anything, check the game's browser to see how many gigs it adds up to. Some recent titles advertise smaller file sizes than people expect. And if in three months you're already bored with the typical stuff, you probably need to step outside the mainstream and explore weirder or niche things; that's usually what hooks people the most in the long run.