I happen to have Brawl's ST on iPod (shh) so I have a lot of experience in this topic. :D
My favourites shift and change but I have a few that have always been favourites. 'Onett' and 'Pollyanna' from melee's OST in Brawl (I know it's confusing hey?) are two big favourites. So is Brawl - melee's 'Fire Emblem' song. I love the SSE's boss battle theme (fun fact; doesn't play in the 'boss battles' mode but only sometimes in the actual SSE!) and i'm a sucker for 'Village of the blue maiden' (zelda), probably due to the fact that the Kakariko village theme is one of zelda's most iconic tracks and a beautifully simplistic yet fun melody that you can do a lot with. Others go in and out. From each series atm, I love:
Mario:
- Super Mario World title/ending credits
- Delfino Plaza
- Bob-omb Battlefield
- Luigi raceway
- Overworld remix theme
DK:
- Overworld map for DKC
- Bramble Blast
- Battle for storm hill
- Jungle racing level
- 80's DK main theme
- DK Jungle Hijinx (one of the most iconic VGM known to everyone
)
Zelda:
- Tal tal heights
- Dragon Roost Island
- The great blue seas
- Village of the blue maiden
- hidden village (TP)
- Molgera Battle
Metroid:
- Ending theme
- Theme of Samus
- Metroid Prime main theme
- Norfair
Yoshi:
- literally like, everything, both from melee and brawl!
Kirby:
- Again, pretty much everything except frozen hillside and even then I don't actually mind that song so...
Starfox:
- Main theme
- Corneria
- Venom (melee)
- Star wolf's theme (and the spanish remix!)
- Space Armada
Pokemon:
- Main theme
- Route 1
- Victory road
- Pokecenter theme
- Gym theme
- Dialga/Palkia battle
- Team Galaxy theme
F-Zero:
- Mute city (both brawl and melee)
- Big blue
- Fire field
- get up and get the last chance!
- some others, can't remember atm
Fire Emblem:
- Main theme
- Medley
- Power-hungry fool (so, so much! :D)
- Winning road
- Victory is at hand!
- Eternal bond
Earthbound:
- Like, everything.... :D :D :D :D EB music, especially melee's music is soooo good!
Pikmin:
- Main theme of Pikmin
- Pikmin 1/2 stage clear/day end
- Pikmin 2 world map
- Environment ambience (I mean hey why not?
)
WarioWare:
- Main theme
- Mona pizza (both JP and ENG)
- Mike's theme (prefer JP)
- Ashley's song (prefer JP but english isn't bad)
Sonic the hedgePowehog:
- Green hill zone
- I like quite a few of these other songs but more in a cute way: They're fun to listen to but I don't generally listen to them a gigantic heap
Metal Gear:
- Theme of love (lol Pirates of the Caribbean theme I see you hiding!
)
- MGS II main theme (builds up really nicely and is a fun throwback!)
- a few of the others, can't quite remember atm
Other:
- Golden sun boss battle medley (YES SO MUCH!!! :D)
- Tetris (both type A and B)
- Shin Onigashima
- Mii channel theme
- Mario golf/tennis theme
- Panel de pon's theme
- Pictochat (random and fun!)
- G&W flat zone 2
- Clu clu land
- Ice mountain (prefer melee's)
- Famicom medley
- Gyromite
- Dr. Mario
- Power-up: wrecking crew
- Title: big brain academy
- Wii sports title
Smash Brothers:
- SSB 64 credits
- SSE Boss battle theme
- Tabuu (final boss battle theme)
- Subspace theme
- Melee main theme
- Melee Giga Bowser
- some others
I think that's my main list right now. I know i'm forgetting some, so i'm sure there are plenty of others I could add to that list but those are my favourites right now. I used to like some others, most of them i've liked from the word go or early on (see - 'Clu clu land'!), some are late additions (A lot of Fire Emblem) but all are fun and awesome to listen to IMO.
