Each of the historical geniuses we might consider was (as another commenter aptly mentioned) limited by the science and materials available.
When we, for example, consider Da Vinci, we must wonder (@paul1967 ) what he might have accomplished if he were brought forward in time
There is, as well, a school of thought that when it is possible to invent a "thing", it is almost certain to be done. (Airplanes and TVs and radios etc were conceived of and invented in various places by people, pretty much unconnected with each other)
With Tesla, however, I concur with @RobLawrence . even tho we'll never know the huge missing parts of his research, he had to be amazingly beyond any level we can imagine.

If someone steals a Tesla car should we call him an Edison car thief?

Can you imagine what he could accomplish with today's technology.

true genious

Bowie did a great Tesla: