If you didn't sell Mario Odyssey, give it another shot. Sometimes games need a few shots at it. My brother started and stopped playing BOTW twice not really liking it before trying a 3rd time and loving it. I've done the same on quite a few games like Skyrim, Final Fantasy X, Grand Theft Auto 5. It really is the perfect 3d Mario game and quite addicting once it hits its groove. If not that's cool, not every game is for everyone. I personally can't get into Halo, Call of Duty, most free to play games, and many other popular games that just don't click with me.
Most people love Odyssey, including me, but yeah for sure not every popular game is loved by everyone. I for one find GTA boring, couldn't get into Minecraft and Fortnite. People who don't like Odyssey seem to just not like open level 3D platformers. They want platformers that are more like linear levels like the 2D variety. That's the only complaint I've ever seen of Odyssey. They tend to like 3D World and Galaxy but not SM64, Sunshine, and Odyssey.
Super Mario RPG 2. Bring back the cast, bring back the Smithy Gang with a new leader, bring back Geno and Mallow and Bowser and Peach, add Toad and Luigi and Yoshi and 2 more new characters for a proper RPG style cast (with the ability to swap characters out like in FFX).
Oh, and Super Mario Galaxy 2. Another GOOD yoshi's Island, and another GOOD 2D Platformer. Mario has only had 3 great 2D platformers (3, World, and NSMB U...yeah I know I'm weird for thinking that...it's the world maps)
Oh my god, weird for thinking that is right haha. NSMBU is I'd say the worst 2D Mario I've ever played by a long shot, in that it is pretty mediocre, while all other 2D Mario's are pretty fantastic. NSMBUD is a lot of fun multiplayer, but I had to force myself a bit to keep playing through it one player to beat the game.
That's just it, though...it had so much more to offer than any other 2D Mario outside of Super Mario World or Super Mario 3. It had the most unique and interesting level design maybe of any 2D Mario, it had the most secrets, it had dozens of alternate exists and hidden routes, it had plenty of ways to enjoy the game, there was actual interaction on the world map, etc.
It was by far the most innovative, fun, and creative 2D Mario since Super Mario World. (I don't count Yoshi's Island, that's its own thing and it's wonderful). I used to think it was mediocre as well, but after learning a bit about level design through Design Doc and GameMakers Toolkit, I came to realize just how great the game's level design really is. I dunno, that's a hill I'm willing to die on. NSMB U and NSMB UD are some of the best 2D Mario has ever been and I was happy to pay full price to get them on Switch even after buying the game and expansion on WiiU.
My Console Library:
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android
Top 6 this generation:
Bloodborne, Sekiro: Shadows Die Twice, God of War, The Legend of Zelda: Breath of the Wild, Dark Souls III, Red Dead Redemption II, Rock Band 4