Two observations:
First, if you listen to a lot of artists talk about their biggest hits, they are often songs they wrote very quickly. Trent Reznor recently did an interview (it's on YouTube) where he was talking about "Head Like a Hole". He spent a lot of time working on other songs for the Pretty Hate Machine album, but HLAH came together in just a few hours at the end of the time he had to work on that album. He sort of dismissed that song because he didn't feel like it had "earned" a spot as the single for that album. There were other songs he had spent a lot more hours working on and he felt a greater connection to those songs than HLAH.
He had a few days to work with the producer Flood at the end of the process. Flood immediately said HLAH should be the lead single from the album. Trent pushed back, but Flood told him it doesn't matter how much time you spent working on a song - the hit is the hit. I've heard similar versions of that same story from a bunch of rock and pop artists over the years. Often times the most successful songs just sort of fall out of the writer's mind in a matter of an hour or so.
Second, I have a personal theory: I think music is a lot like a skill tree in an RPG style video game. I think there are three different areas of expertise in music - Technique, Composition, and Presentation. If you want to become really good at any of these different skills, you have to put a lot of time into them. But the time and energy you put into one of them is a sacrifice for the other two.
Technique would be how technically skilled you are at your instrument, such as a guitar player who can do all the crazy shredding or a drummer who's able to play really complex rhythms in odd time signatures (Thomas Haake of Meshuggah, or Mike Portnoy of Dream Theater). Each person probably starts with some level of potential, but even if you're a prodigy, you still have to put in the thousands of hours to become a master at the technique of your instrument.
Composition would be the ability to write songs that connect with people. One of my favorite examples is Kurt Cobain of Nirvana. Go listen to "Smells Like Teen Spirit" - it's the most ridiculously simple guitar based song ever. The verse is literally him strumming two open strings. But even though that song is so stupidly simple, it became an anthem for a whole generation of people. If you play the first 3 seconds of that song on a guitar, hundreds of millions of people around the world could recognize it. The point here is you can have amazing technique, but have no talent for writing music that connects with people. Think about all the amazing orchestra players who are masters at learning difficult pieces. How many of them have gone on to write music that connect with as many people as "Smells Like Teen Spirit"?
Presentation is it's own skill. I always think of Kiss as a great example. None of the members of Kiss were great players (technique), and while they were decent composers, the thing that really made Kiss the big act that they became was their costumes, their live shows, all the antics and related media around their band. If Kiss had just been four average dudes in regular clothes playing that music, they wouldn't have become the global mega-stars they eventually became. The presentation of Kiss is as much or more a part of the band than the music.
So you might have the natural talent to be a great Technique player at a given instrument, but have no talent for Composition. Or maybe you've got a great vision for the Presentation of a type of music, but you're not good at the Technique or the Composition. Each individual or group of people working together has to find what their strengths are.
If someone is sufficiently skilled at one of these things, it's possible to find outside people to help them fill in the other two. I think the people we tend to resent in modern music are people who use their good looks for the Presentation portion, but they hire song writers and players with good technique to back them up. We can point to plenty of pop stars who's entire career are based on them looking pretty in front of a camera and on stage (both genders). They don't write his music or lyrics, the record company hires people to do that for them. They don't do anything impressive with their voice as a singer. Without a whole company of people around them, they wouldn't be a star. Really, they're a performer similar to an actor. They're performing at their role in this larger machine that is their pop star image.
The people who are really shocking are the ones who are amazing at all three of these skills. The best example I can think of here is Michael Jackson. Put all the controversy aside for a second and just think about him as a musician. He wrote almost all of the parts for his big hits by essentially singing the melodies and almost beat-boxing the drum parts. Then he wrote the vocal melodies and lyrics and recorded those over the top to create demo tapes. He would bring these demo tapes to producers who would translate his melodies, bass lines, and drums into instruments like synths, drum machines, etc. It took an incredible amount of Technique and Composition to start with nothing and wind up with the Off the Wall, Thriller, and Bad albums. Now think about his Presentation: We can poke fun at the white rhinestone glove and his short pants with white socks, but go back and watch that video of the first time he did the moonwalk dance to Billie Jean in front of a live audience. That was completely shocking. As a kid during the 80's and 90's, I remember his music videos were events. They would do countdowns for days to a world premier on prime time network TV.
/rant
