I think the Special Relativity Theory would have been discovered without Einstein. Both Poincare and Lorentz were very close. Sooner or later somebody would also have had the idea that the ether is unnecessary and overcomplicating the description of electromagnetic phenomena. Concerning General Relativity I have my doubt whether it would have been discovered as soon as 1915, if Einstein wouldn't have followed the track for more than 12 years. Planck even suggested to Einstein, he shouldn't bother about gravity too much, because he thought it would be too complicated a task with little impact for physics. The latter was perhaps true at the time, but for sure it's not true a bit later when the Hubble expansion (another example for a misnomer, because it should rather be named Lemaitre-Hubble expansion or, as I learned from this great Insights article, Lundmark-Lemaitre-Hubble expansion).
On the other hand, I'm sure that Vera Rubin should get the Nobel for her work on the rotation curves of galaxies. I guess, however, she'll have to wait until it's clarified what dark matter is, i.e., the earliest when dark-matter candidate particles are discovered.
The Nobel prize for Einstein is also an interesting story. Ironically, he got it for the only work which is outdated today. The photoelectric effect in the sense Einstein analyzed it in his famous 1905 paper is not due to the quantization of the electromagnetic field but due to the quantization of bound electrons (see my own Insights article on the subject), and photons have very little in common with classical particles, even less than other quanta that have a non-vanishing mass. The wave-particle dualism is obsolete with the discovery of modern quantum theory in 1925.
Of course, the Nobel committee was very right to give a Nobel to Einstein. If a single person deserved the prize at his time it was Einstein for his very broad spectrum of groundbreaking research in theoretical physics. Of course, the most important work was General Relativity, and he should have gotten the prize for this work. However, the theory was much more controversial than today. It's very interesting that not physics arguments lead to the decision of the Nobel Committee but the criticism from philosophy! Particularly Bergson's cirticism of the idea of time in relativity lead to doubts about the validity of the theory, and thus the Nobel Committee decided to give Einstein the prize for some other achievement, and they decided for the explanation of the photoeffect. Concerning this interesting story about Einstein's Nobel Prize, see the book
J. Canales, The Physicist and the Philosopher, Princeton University Press (2015)