Depends what your goal is as well, I've no interest in creating a startup with the potential to be a huge company, 1) those ideas are really hard to come by 2) they will inevitably attract competition 3) unless they are not trivial well funded competition can and probably will catch you rapidly 4) first mover advantage works on a product that has network effects but not much else.

The product I want to build next is a niche product for a very specific (but quite large in absolute) terms demographic, profit per user (after tax/VAT/Hosting minus staff) is approx $6 per month, at 500 users I'd be doubling my current income, at a 1000 I'd be able to work on it full time, at 2000 I'd be very comfortable, anymore than that would just be gravy.

It's not even a difficult build (I've built much more complex projects for clients) but the market doesn't exist at all (which means it's either a really good idea (unlikely) or a terrible idea (more likely)).

In either case I'm gonna give it a shot since it's a product I'd have bought if it existed immediately and happily.