It's interesting for me to look at your boss's "Good ideas" circle, because for me, Amazon was an obviously bad idea, Uber is still a bad idea, and I thought DropBox was a good idea but when I look at their initial Show HN a good number of other people did not.
I think the problem we all suffer from is that we all have a very limited perspective. Things that we think are bad ideas - because we don't have an immediate need for them, or because we don't understand them - may be an obvious good idea for someone sitting somewhere else. And the trick to picking good startups is to get out of that personal bubble, and understand what is it about the users of that startup that differs from us, and whether that characteristic is going to be shared by more people in the future.
I think the problem we all suffer from is that we all have a very limited perspective. Things that we think are bad ideas - because we don't have an immediate need for them, or because we don't understand them - may be an obvious good idea for someone sitting somewhere else. And the trick to picking good startups is to get out of that personal bubble, and understand what is it about the users of that startup that differs from us, and whether that characteristic is going to be shared by more people in the future.