Galaxy is more like an enclosed parkour while Odyssey has openworld stages.

I gotta give it to the Galaxy series personally; they are two of the finest video games ever crafted in my opinion with their endlessly creative stage design, perfect controls, and sublime soundtracks.

Next comes the exploratory ones; 64 and Odyssey are great, but Sunshine's mediocrity drags the average down.

3D World/Land were good games, but didn't feel as imaginative or epic as the rest. (Sans Sunshine)

I'm going to disagree with that last line. 3D World had a very traditional format, but I think they knocked it out of the park with the creative twists they put on the standard platforming levels. Lots of gimmicks, and I mean that in a good way. Not quite up to the standards of Galaxy, but pretty close imo.

3D World definitely did have some cool ideas like the double cherry, the glass pipes, and the cat suit, I just feel like the levels, while very well designed, were a little simple. Like I say, still a good game though.

They were simple, but I think that's part of the point of the 3D Series. To recapture the more simplistic style of the 2D Mario games. To me, the 3D World series is what Mario would have been if Nintendo went the same route as Crash Bandicoot, taking the traditional platform game and putting it into a 3D style. Personally I'd love to see them continue with all three subseries since they all scratch a different itch.

I don't strictly disagree, I guess I just feel like 3D Mario is best when it embraces more sophisticated level designs either through the gravity antics of the Galaxy series or the sandbox playgrounds of 64 and Odyssey. 

I do like Mario 64 and Galaxy 1/2 better. Odyssey is about equal in my book. Something about Odyssey just didn't quite click with me. I think they went a little overboard. It's a little hard to get excited about getting a moon when there are 800 of them. It feels a bit off when the reward for doing the hardest segments (like the Bullet bill bridge thingy) gets you the same reward as "throw your hat at that glowy thing". I think they need a better way to make harder achievements feel more rewarding. 

Galaxy's gravity mechanics let them get more creative, but it really wouldn't have worked for well for multiplayer. The generally shorter levels also make it a bit better as a pick up and play game. 

As someone who avoids the harder challenges and didn't go for 100% completion I didn't have that problem with Odyssey myself, just due to the kind of gamer I am. I liked being able to rack up 5-6 moons in a 30-40 minute session, made it feel like I was always making progress, but that's just me, I can kinda see how it might not be as satisfying for a completionist. 

And I don't do multiplayer, so I kinda felt like having to accommodate 4 players made 3D World's levels a little less engaging as solo experiences compared to other 3D Mario games.

Outside Sunshine, I prefer the exploratory subseries because it distinguishes itself much more from the 2D games and it gives me a sense of adventure that I don't get from other Mario games + Mario's agility and move set in these games is top notch.

64/Sunshine/Odyssey - the exploration aspect is what makes a 3D Mario for me. The others are fun extensions of the 2D franchise in 3D.