Apart from the iconic W1-1 music (which isn't really a theme), here is a theme which defines Mario.

in Super Mario Bros:

in Super Mario Bros. 3:

and Super Mario 64 (from 0:39):

and Paper Mario:

So beautiful. *sniff*

Does Mario Galaxy have this theme?
...I'm going to play Galaxy again, if only to listen to the beautiful music.

I don't think so, but the Good Egg, Gateway, Space Junk, Gusty Garden, Melty Molten, Buoy Base, Ghostly, and Star Festival music more than make up for it. And of course the credits music which is all of the above.

I love Pokemon, Kirby and Metroid music too, but have yet to find a non-Nintendo game that I like the music to.

I always considered the W1-1 music Mario's theme...

wow I never noticed that them was recurring in that many games.

Interesting find.

Paper mario had the best version! :)

Super Mario 64's made me cry. No, really.

No, It's still the World 1-1 Music in Super Mario Bros. 1.
Nice find though.

Yeah, but listning to the Paper Mario version during the games eding scenes is very heart moving... :)