That's already in the game:

If Shadow Moses Island does return I think Zanzibar Breeze and Theme of Solid Snake would make nice alt tracks
Also this:

~ Let the Battles begin!

~ Grand Finale: Mario and Luigi: Bowser's Inside Story

~ Gerudo Valley

Let me give a crack at it. So black titles are the original track, red titles are remixed tracks and blue titles are original remixes.


Paper Mario 64 Final Boss Theme


Desperate Assault
Trouble Erupts!
A Dangerous New Enemy


Nube Negra


Zero-Two
Gourmet Race


Hyrule Castle [Breath of the Wild]
Great King of Evil: Ganondorf
Ganon
Song of Healing
Majora's Wrath


L'Oscurita del'Ignotto
Graceful Assassin
Graceful Assassin GBA
Rage Awakened

Others I think would be kind of cool okay?:

Darkstalkers series:
Theme of Morrigan
Theme of Demitri
Theme of Jedah

Resident Evil series:
Super Tyrant [Resident Evil 2]
Final Metamorphosis [Resident Evil 3: Nemesis]
Theme of Leon S. Kennedy [Resident Evil 4]
Heat on Beat 2013 [Resident Evil 6]
Heat on Beat 2015 [Revelations 2]
Heat on Beat 2018
Garage [Resident Evil 7]
Nightmare Wave 3 [Resident Evil 7]
Nightmare Wave 5 [Resident Evil 7]

Silent Hill series:
Red Pyramids
Kill God [Silent Hill 3]

Overwatch:
King's Row

Rage Awakened Kingdom Hearts 2.5 Remix
Desire for All That is Lost Kingdom Hearts 2.5 Remix
Threats of the Land (Battle Medley) Kingdom Hearts Orchestra World Tour
Let Darkness Assemble Kingdom Hearts Orchestra World Tour

FoD

Oh boy, here we go...




Anything from the Galaxy games really
The Bowser's Trap remix used in Super Mario 63
MKWii Bowser's Castle
Some Paper Mario 2 stuff
keeping this short because I have way too many ideas




Hyrule Castle Medley (BotW)
Attack on Divine Beast Vah Ruta (BotW)
Spirit Tracks Finals Boss Theme (ST... duh)
Hyrule Field (TP)
The Great Sea (WW)
Dragon Roost Island (WW)
Eclipse of the Sun (HW)
I bet SS had some awesome tracks too but I cant remember any rn. Gotta play that game again sometime soon...




Vs. Champion (Kanto) (B2/W2)
Vs. Team Rocket
Vs. Cynthia (You thought this was just a regular house in Ondula, but..)
Vs. Diantha
Vs. Gym Leader Medley (including the Final Pokemon section of Gen 5)
Route 209 (D/P/Pt)
Route 10 (B/W)
Vs. Rival (OR/AS)
The entiretry of the Pokemon Mystery Dungeon series soundtrack




King Dedede's Theme (SSBB)
Masked Dedede (Triple Deluxe)
Sullied Grace (Triple Deluxe)
idk I never played a Kirby game




Dark Samus Remix
Diggernaut (Samus Returns)
Chykka (MP2, both variants)
Vs. Hive Mecha (MP)
Rundas's Theme (MP3)
Title Screen/Menu Theme (MP2)
Metroid Prime Series Medley
SR-388 overworld (Samus Returns/Return of Samus)
and so so many more




Rocketbarrel (DKCR)
The amazing songs from DKCTF that I forgot again because I have never played the game myself even though I own it





Egg Fleet/Final Fortress Medley (Heroes)
Hill Top Zone (Sonic 2)
Rooftop Run - Day (Generations)
something something Colours


subject to be expanded in the future, but thats it for now

yeah can we specifically get boss 02, defy the legends, dark matter or dialga's fight to the finish

Hikari
Fountain of dreams
Route 1

Or Sky Tower, Temporal Tower, Vast Dark Ice Mountain, the PMD main theme, Tree of Life, the track of the very first future dungeon in Explorers that I keep forgetting, etc etc etc. Hence why I want them all

I just want them to bring back the Yoshi Island remix from 0.9a. It was so bright and energetic, I loved the actual island vibe it had with the xylophone, drums and wood knocking in the beat, reminds me of the festival songs we would do in school in Jamaica, but more calypso like and less Kete drum based. I just love it.

Also, I don't know how they could do it, but some way some how, I want the Full Metal Alchemist Opening - Melissa to be in the game. I don't know what the corelation will be, I don't know what stage, but I know that I want it.

That's good, but I prefer for Rewrite from the Opening 4th of Full Metal Alchemist if, Edward Elric and his home stage FMA stage was in the SSF2 game.

I loooove Rewrite as well, but I think Melissa would work better since it was the first opening and that song was on a kind of well known Flash game/movie on Newgrounds, so it will definitely raise people's antennas.

That's not a remix
Ever play Brawl?
Or Smash 3DS?
Yoshi's Island.
Obstacle Course (Spring/Summer)
Right there, buck-o
Everyone thought the Kid Icarus theme in Palutena's Shrine was an original remix too, that one's from Brawl
Check yer heckin' FACTS