As far as I'm concerned, Mario & Luigi 2 and Metroid Dread fill much-needed gaps in the DS's library and warrant sequels.
And I don't care what you say, I can't get enough of Metroid. There have been at most 2 Metroid games per platform so far... I don't see how you can label it as over-prolific unless you're comparing it to its period of dearth, when, need I remind you, everybody was bitching at Nintendo to make more of them.