Im glad to see someone made this thrad! One of the themes i'd like to hear in the new Smash is the remix of Green Hill Zone they did in Sonic Generations. They already had the original theme in Brawl, so i think i'd be nice if they had this version included in the game.
Also, i really loved Sonic Unleashed and i wouldn't mind them using any theme they used from it. Though, it seems like Endless Possibility might be what they use in Smash 4. I'd still like to see other themes used in the game like Spagonia's rooftop run theme or even Eggman's Boss Battle theme.
As for Sonic and the Black Knight, i'd love for theme to use Through the Fire. It's the theme that played when you fight the knights of the round table. Though, i can see them using Knight of the Wind as well.
And for Sonic Colors, i'd love for them to use Aquarium Park Act 1!
Im also curious to see if the 3DS version and Wii U version will include the same soundtracks? Something tells me the 3DS version wont and instead will use more handheld related themes from games like Sonic Advance, Sonic Rush, and the handheld adaptions of Sonic Colors and Sonic Lost World.