Helldivers 2 for me.
I enjoyed the original but was fairly described as typical, while the sequel also looked very similar and generic to many other shooter games out there so why would this have been no different, gameplay and success-wise. But they proved us wrong.
I already knew Palworld would've been a success. It was riding on the coattail of a beloved franchise with its own twisted take. Also the idea of incorporating similar Pokemon designs into their Pal make it more intriguing to many. If it had created monsters completely original then it may not have gathered as much buzz as it did.