Incredible Hulk has surely jumped to top of mind for many people. By the tried and true "one set of track = one credit" method, it is a new ride; however the manner in which is was replaced, with every last inch remaining the same puts the coaster in a gray zone of cred whore vs. sensible human being.
Racing roller coasters are often debated, especially those that are the same structure, such as Gemini or American Eagle. I've always leaned towards one track = one credit, as the ride can still operate with only one side operational. Though the argument of the intent of the ride to act as one is certainly true.
Overall, I always go back to the singular question: "Was this meant to be a roller coaster?" As we just experienced with the Six Flags Larson Loopers and Cedar Fair Disk'Os - some rides can be advertised as roller coasters, yet still miss inherent roller coaster qualities outside of the obvious question of track elements, gravity sections, etc.