Personally I would post just about every track ever here, but one of the best for me is Route 120 from R/S/E - it's so triumphant, and really has a sense of adventure to it.
Another "adventure-y" song is Route 38 from Crystal (and G/S too I guess) which remained stuck in my head for years - my mother heard me humming it ages after I stopped playing Crystal and said she remembered me humming along back then too, lol.
I'd also add all of Colloseum's soundtrack.
Perhaps later I'll post some songs from spinoffs like Ranger.
For now, have this:
No really, listen to it, even if it's from the typing game!