Games I feel would work well as a one off and don't need to be sequel milked:
Stardew Valley - Amazing as it is and it's the passion project of the developer. Once he's done with it, he needs to take a break then make something totally different as not to burn himself out.
Cuphead - A great concept and everything about it is great, as a boss rush style game. Without any major changes to the forumula, there's no need for more of the same.
Octopath Traveler - As much as I want a sequel for this game, I think it does not need one. Sure there is no proper end to the story outside the end of the 8 individual character stories. One of the major let downs of the game. Past that, if you can accept the game is 8x short story, it's really amazing. In too many ways to mention here. I think it's good enough as a one off.
Shovel Knight - Assuming it's one game with 3x DLC. Everything has been said and done here. Even Yacht Club want to move on from Shovel Knight. On to bigger and better things.
Games I felt didn't need the sequels they got.
Plants vs Zombies - The first game was amazing. The sequels were all ruined by EA's micro transactions.
Battletoads - The NES original, though the wrong kind of hard, was still an amazing game, from a gameplay and tech point of view. Every single sequel, including the new Xbox game have been and/or look like garbage. Even the crossover games with Double Dragon were alright but honestly didn't need to exist either.
Chronotrigger - I think everyone agrees this is a good game. Not the best SNES game or the best SNES RPG in my opinion but still very good. The sequels, like
Chrono Cross were just outright terrible. That's why I just stick with Trigger. Sure it's an overcompllicated mess of a storyline but it manages to just be understandable enough to be a great game.
Shadowgate - The NES original was a bailliant early style point and click adventure game. I played the N64 game and it was honestly terrible. I've not played the remake of the original yet but I do want to. Just remaking old games "because you can", be it in 3D or in prettier colours is honestly a waste of time and money. Sure if you can bring something new and better to the game in a remake/remaster then sure go ahead. However the N64 sequel (of sorts) did not of that.
Galaxy 2 did and still does feel to me like a lazy effort by Nintendo to capitalize on their success with Galaxy 1 (which I honestly can't blame them for; they're a business that needs to make money to stay afloat).
To explain the full story to those who don't know. Nintendo had planned to have DLC for Mario Galaxy. They worked on that. At the end of the process they had so much DLC made that Nintendo made the decision to release all the levels they made as a sequel instead of DLC for the first game.
In my opinion the DLC would have cost $20 less than the original game. It might have required the base game to play or or might have been like NSMBU where the Luigi DLC was standalone or like the Xenoblade Chronicles 2 DLC was also standalone.
Maybe Nintendo should have called it standalone DLC instead of Mario Galaxy 2?