It depends on what you are asking about.

For example:

If Newton didn't invent calculus no big deal because Leibniz discovered it also. I'm not going to go too far into the controversy because I believe there is enough evidence that Leibniz did not base his work on Newton though he may have been helped by Newton's findings. Although we must still be grateful for what Newton did with Calculus in developing Newtonian Physics.

Edison wasn't the first to develop the incandescent bulb. He viewed a working bulb with a very short life that inspired him to work on making a longer lasting bulb. There's a good chance that somebody else would have eventually worked out the solution to a long lasting bulb.

On the other hand Einstein's Theory of Relativity was a breakthrough lauded by many prominent scientists who admitted they had never considered the concept as Einstein did. Somebody may have figured it out eventually but it's not guaranteed.

Sorry, but your submission has been removed because we don't allow hypothetical questions. This sort of thing is better suited for /r/historicalwhatif.