Pokemon Diamond and Pearl remake 2021 (someone you have given little importance to has already revealed the name):
1) Sinnnoh region in 3d but not in free-camera.
2) blue Dynamax and Gigantamax
3) Dialga and Palkia "NeoReversion"
4) Giratina two gigantamax form (blue and normal)
5) Arceus new "adaptation"
6) Pokemon in the overworld
7) Free-room underground
8) Underground adapted to the role of wilde areas
9) "Explanation of the origin of the dynamax blue" - secondary plot
10) Library of Canalave City adapted for the secondary plot
11) Difficulty significantly lowered
12) Mega evolutions absent
13) New characters
14) New Unown Event
15) Battle Frontier absent
16) Mt absent
17) Mount system absent
Mt system absent
18) Giants
Good game even if you won't be able to catch them all!