Here are ways that you can win extra belts for your normal or created Superstar in Career Mode.

Belt	How to unlock
ECW Championship path	Clear the Intercontinental Championship path.
Hardcore Championship belt	Clear the Hardcore Championship path.
Hardcore Championship path	Clear the United States Championship path.
United States Championship path	Clear the Intercontinental Championship path.
World Heavyweight Championship path	Clear the Hardcore Championship path.
WWE Championship path	Clear the Hardcore Championship path.