I like your thought process. I guess the $100k mark was just to get ideas flowing. I would like to aim for $100M, but I can't think of a product or service people demand that would achieve that revenue (at least not within my skillset)
How to aim for $100M? Try something crazy, something that other people will look at you suspiciously and whisper he's crazy is he?
Why? Because where is crazyness, there is magic and you will be the only one there, because somehow humans don't like to do crazy things, they like to stay within the norm, not create too much noise.
To become really successful, you need to be 1 out of a million. Some might it's very hard to become 1 out of a million. However, it's very easy if you're trying to do something crazy and that's all you need.
As for what to do, try to find a big problem that can be solved with a nice and sweet app that can be built within 2 months. It doesn't have to be hard to build, it can just be a little app, but you need to try to look for magic.
An example would be Snapchat, super weird, crazy, tiny app, magic.
Hope that helped.
Just get out there and find out what problems people have. Ask a bunch of people which websites/apps drive them crazy.
With a bit of luck they will mention ones that they use regularly or pay money for. Once you find a niche product idea, come up with a way you can test your hypothesis, Lean Startup style.
The unsolved problem space that is solved by building a website is shrinking year over year. It would seem obvious that you need a larger skill set to solve problems no one has attempted yet.