Ideas are not great by themselves. Ideas are only great because someone executed on that idea. Also, ideas are great within some context. The idea of flying on the 1600s would have had you accused of witchcraft (bad idea) but the Wright Bothers executed on the idea, resulting in airplanes (great idea).

In general, ideas are easy to create and essentially free. They become great because of the time, energy, and determination of people.

What you could do to generate possible ideas is take an bland industry and challenge the assumptions around that industry. From the assumption challenges will come the seeds to create a statrtup with potential. But the greatness will only come from people tackling those initial idea seeds.