In my experience a key differentiator is passion. Folks who are passionate about a subject will typically explore it more, and thus have a wider array of experiences and tools to draw on. This makes them able to solve problems others cannot.
It's not so much that the others couldn't ever do it, but they might simply not know enough to ask the right questions to get started or similar.
It's not a 1:1 correspondence, but it is in my view a strong signal.
That said, there are many different aspects to being a good engineer, and most are stronger in some and weaker in others. A good team has a good mix.