I think that it's impossible to know what track is exactly, but I guessed 13 games. I missed the Sunshine (I never really played) and AllStars, I don't consider it a separate game, but fair enough.
Here is my list of guesses (I was typing this comment while watching the video): Don't read until you've watched the video because I'm confirmed these are (technically) the right answers. Intro: Hammer Bros. Battle (Super Mario Bros. 3, NES) 1. Dire Dire Docks (Super Mario 64, N64) 2. Character Select (Super Mario Bros. 2, NES) 3. Secret Level (Super Mario Sunshine, GCN) 4. Overworld (Super Mario Land 2: Six Golden Coins, Gameboy) 5. Overworld (Super Mario World 2: Yoshi's Island, SNES) 6. Good Egg Galaxy (Super Mario Galaxy, Wii) 7. Cascade Kingdom (8-bit) (Super Mario Odyssey, Switch) 8. Super Bell Hill (Super Mario 3D World, Wii U/Switch) 9. Castle (Super Mario Bros., NES) 10. Walking the Plains/Overworld (New Super Mario Bros. Wii, Wii/New Super Mario Bros. 2, 3DS) 11. Underwater (Super Mario Bros. 3, NES) 12. Underground (Super Mario Land 2: Six Golden Coins, GB) 13. Title Screen (Super Mario All-Stars, SNES/Wii) 14. Underground/Cave (Super Mario World, SNES) 15. Overworld (Super Mario 3D Land, 3DS) Outro Theme: World Bowser (Super Mario 3D World, Wii U/Switch) Correct: 15/15
Hmmm...that's actually a pretty good question. I thought I may have used the Super Mario 64 DS track by accident, but I think that's nearly identical to the original. This one seems to lack the reverb of the original track. Impressed you could tell the difference!