Some popular musicians who make it to the top all have one secret to success in common- they were classically trained. They probably sat hunched and frustrated over theory papers and lost sleep the night before exams, just like you. I am not referring here to people who make it through the Simon Cowell pop factory with an army of vocal coaches and songwriters, I’m talking about the people who made it to the top through sheer musical ability and determination.

Although he is mostly known as a jazz/pop musician, Jamie Cullum can not only play the piano, but also guitar and drums. He’s another one who’s clearly spent a lot of time practicing and knows all about notes and things. http://www.youtube.com/watch?v=srNkCHB3MSQ
There are others; Hearsay’s Myleene Klass studied the piano, violin and voice at the Royal Academy and Annie Lennox studied the flute there too. Going back even further, most of the Electric Light Orchestra were classically trained, too.
Daft Punk actually wrote a half classical, half modern score for the film Tron: Legacy. Its one of my personal favourites, especially for the big brass sounds towards the end of the film. http://www.youtube.com/watch?v=MeqeWF8pkAE These are contrasted by Daft Punk’s signature electronic sounds in other parts of the film. Awesome. http://www.youtube.com/watch?v=M4dUiBfMQVU Strangely, Pharrell Williams wasn’t invited to this one…
In short, yes, Grade 5 Theory could get you a Brit award, so don’t forget to learn your cadences!
p.s. If you know any I’ve missed, stick a comment below.