As of writing this (3:26PM CST 10/22/2024) I haven't gotten to Shadow Generations yet, but the Sonic Generations portion is pretty solid. I don't like some of the dialogue rewrites and having the drop dash as modern sonic is a little weird, but you get used to it after a while.
EDIT (9:20 am CST 12/5/2024) I finished the game. This was awesome. Would play again.
Now I do have an issue where the game basically freezes every now and then when an object loads in but that could just be my computer's slow processor, so I don't blame the game.