The main things are a huge (ideally uncontested) potential market and a sustainable competitive advantage (i.e. moat). This means it's VRINE - valuable, rare, inimitable (can't be copied), non-substitutable (nothing else will do), exploitable (people will pay for it).

What is VRINE may be proprietary technology (ideally patented), key strategic partners (e.g. suppliers, distributors, collaborators), or perhaps brand if you're first to market. You also need the relevant resources and capabilities (i.e. skills) to be able to make it happen or attract people who can help you.

You should be at the leading edge of a new trend before other people are aware of it so you can become the dominant product ("blue ocean") and become associated with the product category itself. However, this is easier said than done since innovation is often messy, with no clear end point, so agility and learning is key. Also, Apple were consistently second movers, in which case you need a clear differentiator (think Stripe focussing on ease of use, Apple on design, etc.).

You may also want to research value chain reconfiguration. This explains how you can avoid competing head-on in established industries in ways the incumbents just can't respond to rapidly because it cuts against the core of their business model. The classic example is low cost airlines.

These aren't hard and fast rules. But check out the Innovator's Dilemma to see why entrepreneurs will always be needed.