I've come up with many ideas on my own that others have made millions or billions on. The execution is the hard part. There's a quote from someone who eludes me that says,"If you're on the right track, but you're standing still, you'll be run over." The comforting thought you get when this happen is that you come up with good ideas.
My theory for coming up with good ideas is simple. Look at new technologies, and try and apply them to the world. Look at a lot of the first electrical devices, they're just an application of applying spinning motion to a tool creatively. The Internet when it first started getting released to the public, a lot of people figured there would be graphical games, instant messaging, and online stores, but when it first came out, it didn't have those yet. You always look at a new technology and figure how it will change the world.
The Internet still has lots of applications to still be made that people haven't thought of. I think someone's eventually going to make a Real Estate application where anyone can list their place, and have a search for places, and they do the transaction on their own, with some way to confirm the transaction and only charge 200$ for the whole ordeal. So undercutting realtors could be a huge thing. No one has made an application that caught on as the defacto ap for listing your house as a flea market because if so, people could link to their smart phone when they're within X miles of one. There are probably new social media sites that haven't been made. One site I've been thinking of, but can't come up with how to do it right is for PC video gamers to register on to keep in touch with long lost teammates.
So the most common way to invent a new thing is think how new technologies can make life easier, but sometimes prayer works too. I have always been fascinated with AI since the 80s with the movie TRON and stuff. Everyone thought AI would be a computer algorithm go out of control maybe on networks to learn and use the memory. Other people thought AI would be when science invented a pseudo brain. Neither of these are viable ways to start an R&D project because you have no way to gauge progress towards success and failure is almost assured. So I asked God how to make AI. Instantly I thought of a computer that holds a world state in memory that it gathers in through cameras and sensors. Then it can identify the objects in the world, and interacting with them via goals is almost trivial once you have the data in mind since that's how sandbox video games work.
I have an AI site here which shows the building of AI is doable for anyone who would be willing to fund a team Anyway, I wouldn't be surprised if we had AI in 15-30 years if someone started now. I just thought it was cool that I came up with this AI algorithm instantly after praying for it.
