I like all the mainline Mario games quite a lot. I'm a bit surprised by my own list, now that I tried ranking them after how much fun I had with them, combined with the overall impression they made on me.
My top 10:
1. Super Mario Odyssey (Galaxy was probably more jaw-dropping, but Odyssey just has better flow and controls. It's also cooler and more epic! Time will tell if I'll rank it lower with time, as I'm currently 600 moons in.)
2. Super Mario Galaxy (Amazing experience, emotional and creative, fantastic music.)
3. Super Mario World (I grew up with the NES Marios, but this one just controls better and felt more like a real journey.)
4. Super Mario Galaxy 2 (Similar to Galaxy 1, maybe better as a game, but not as fresh or emotional.)
5. New Super Mario/Luigi Bros. U (What can I say, I love what the co-op brings to Mario, and the level design is great.)
6. New Super Mario Bros. Wii (Same reason as above; amazing memories with friends and dates!)
7. Super Mario Sunshine (Extreme freedom and maybe still the best controls in a video game. Possibly topped by Odyssey.)
8. Super Mario 3D World (It still beats Odyssey when it comes to multiplayer, so it's unique that way. Does feel like a "level pack" though, rather than a coherent adventure.)
9. Super Mario Maker (Didn't expect to care for this one, but I became obsessed and spent surely 200 hours on it. Sequel needs multiplayer.)
10. Super Mario 64 (It was jaw-dropping when seeing it in stores before release, but playing it, something just didn't FULLY click with me. The worlds are too simple and empty, or something.)
The rest:
11. Super Mario 3D Land (Fun but simple and very easy.)
12. Super Mario World 2: Yoshi's Island (Wow, I'm putting this low. It used to be my very favorite, but the levels are sooo long, and it bores me nowadays.)
13. Super Mario Land 2 (Although dirt easy and very short, it has some of the most inspiring and original level designs! I wish they'd look at THIS when making the next 2D Mario!)
14. New Super Mario bros. 2 (Quite generic, but co-op was a great experience.)
15. Super Mario Bros. 3 (Yes, I rank it this low. It's good, but I like all the above more. The controls feel limited, the "it's just a stage play" visuals take me out of it. The music makes me a bit uncomfortable.)
16. Super Mario Bros. 2 (I like this game a lot. Just not more than the ones above.)
17. New Super Mario Bros. (Was fresh upon release, but doesn't stand up well because of the superior sequels. Definitely the most "skippable" one.)
18. Super Mario Land (It's fun. Also some cool level design, but it's short and "too small".)
19. Super Mario Bros. (Not a bad game, but it just controls are just much nicer in all the sequels.)
20. Super Mario Bros.: The Lost Levels (Almost the same as SMB, but more frustrating.)
21. Super Mario Run (Didn't buy the full game, but the gameplay is too simple, despite being quite fun to collect the hard coins.)