Because why not. Here are my five favourite tunes features in main Pokémon games up to XY.
Honourable Mention: Santalune Forest (X, Y)
https://www.youtube.com/watch?v=hSGZqdfZj4g
Lovely theme, but not as memorable as 1-5!
#5: Dark Cave (Gold, Silver, Crystal)
https://www.youtube.com/watch?v=vyPamrElGOM
The only time I've ever been happy to trawl through the colourless hell of a cave in a Pokémon game.
#4: Pokémon Contest Reception Hall (Ruby, Sapphire & Emerald)
https://www.youtube.com/watch?v=AZ29daov4o8
I spent a lot of time berry blending and contest entering in Ruby, Sapphire and Emerald, so I heard this a lot. Thankfully, it's exceptional. The Hoenn trumpets are in full force. Sadly didn't like the ORAS version as much.
#3: Versus Legendary Pokémon (Black, White, Black 2, White 2)
https://www.youtube.com/watch?v=QCkmgssjhvo
Legendary hunting for me has never been a tenser, more stressful experience than in Black and White thanks to its excellent theme tune. I'm in love with the bit when the tempo warps.
#2: Route 4 (Red, Blue, Yellow)
https://www.youtube.com/watch?v=hLcJois9yTs
My first Pokémon game was Yellow. Being inexperienced, it meant I spent hours and hours of my young life stuck levelling my Pikachu and nothing else until its normal-type moves could defeat Brock. When I finally did, I was greeted with this theme - and that's a feeling that's embedded deep within me. The Route 4 theme is like nostalgia dropped its trousers and did its business in my ear.
#1: Team Plasma Grunt Theme (Black, White, NOT the BW2 remix)
https://www.youtube.com/watch?v=LB87TndHlFg
GODDAMN, THAT INTRO. It nearly single-handedly made Plasma look like a credible threat instead of the gaggle of spanners that evil teams in Pokémon always are.