I have a question for people who feel this way: when/how did you develop this preference? Was Super Mario 64 the first Mario game you played? Was it your favorite? Did it redefine Mario games for you? Cause none of the Mario games before 64 placed a big emphasis on non-linear exploration. There were branching paths and things like that, but it was pretty straight forward. I loved Mario 64 when I played it in middle school, but it never really felt like "Mario" to me. I'm not saying preferring Mario 64 style games is wrong, I'm just curious about how you all developed that preference.
Mario 64 was my first 3D Mario and still my favourite 3D one, but it wasn't my first Mario (it was World, which is curiously mi favourite 2D Mario ). It's true that 64 and Sunshine have much less platforming and the formula was way different from previous games, but I think it worked really well, and maybe it was this fresh air what really engaged me. I didn't really see the necessity of having the exact same formulas in both 3D and 2D games.
Galaxy still had some quite big levels and backtracking, but Galaxy 2 completely took rid of them. I think 3D Marios should always keep a balance between classic linear platforming and the adventure, the very own trademark of the 3D series since its beginning.