As far as impact. Mario 64 >>>>>>>>>>> 3D World all day. No questions asked. But as far as actual gameplay and what's the better Mario game? To me 3D World is better. I wouldn't be mad if someone preferred Mario 64 tho. It's a classic. Like I said I been playing Mario since the NES. And 3D World is def one of the best in the series.
I liked 64 better. 3D world is a good game, no doubt, but the crazy physics and shenanigans in 64 put that one over the top for me. If anyone doesn't believe me, go watch some Mario 64 speedruns
1, 3, World, Yoshi's Island, and 64 are the GOAT games in the series, IMO. (SMB2 is underrated)
I think the Lost Levels might be my personal favorite (depending on my mood), even though I know it's objectively not the best in the series. That game is crazy.