I don’t think it would be possible for a bad sequel to ruin a game I liked.

Metroid Other M has not ruined previous Metroids for me (its terrible Adam Malkovich depiction doesn’t even register when I’m playing Fusion, since the character has barely any continuity between the two).

Okamiden did not ruin Okami, it just sucked on its own and what little story it tried to change I disregard. I’d replay Okami today in a heartbeat.

Xenoblade Chronicles 2 took a direction I hated, both in style and gameplay, and it made me want to replay XC1. I did. It’s still awesome, though XC3 became my favourite.

And complete opposite of the topic : Baten Kaitos was not bad, but kind of a silly popcorn game to me. Baten Kaitos Origins did not ruin this game : it was so great and flipped the interpretation of the first game so well it made BK better.