Recently, I've started playing Sonic Unleashed again to up my ranks, search for medals, and remind myself why I still play Sonic games.
Many acts are pretty tough and even the most stellar tracks get a bit tiresome for me, which is why I love the background music option the Xbox 360 has. You can play literally whatever song you want whilst enjoying your game.
(The fact this feature was gimped on the Xbox One still pisses me off.)
Anyway, I have playlists of songs I listen to whenever I'm on an act or mission I know is going to take multiple tries or just for the heck of it, one for each continent and form of Sonic's. For example:

Windmill Isle (Hedgehog)

  • Can You Feel the Sunshine
  • Earth, Wind & Fire - September
  • Sunset Hill Zone: Act 1 (Advance 3)
  • The Pillows - Runners High
  • Back 2 Back (Water Palace)
  • Blake Shelton - Bringing Back the Sunshine

Skyscraper Scamper (Werehog)

  • Gorillaz - Rock the House
  • Spring Yard
  • B.B. Rights - Funky Radio
  • Casino Night (Multiplayer)
  • Michael Jackson - Blue Gangsta
  • Star Light
  • Bad Meets Evil - Fast Lane

Those are just examples. Are there any songs you like to listen to in-game?