His most important work was establishing that E=mxc^2 which has contributed greatly to nuclear Physics.
Not really - you can't do any particle physics, nuclear physics, astrophysics, or some of the finer calculations in atomic physics without relativity. The theory is very important - not so much to terrestrial engineering applications, perhaps, but in physics research & theory, and space engineering applications, it is indispensable.
In fact the whole of the theory is based on Lorentz transformations but Einstein put it in an intriguing theory.
True (for special relativity). As I'm sure you know, though, special & general relativity were hardly Einsteins only contributions to physics - they're just his most famous.
His most important work was establishing that E=mxc^2 which has contributed greatly to nuclear Physics.
E = mc2 is a direct consequence of relativity theory.
Anyway, the whole business of ranking Newton against Einstein is kind of silly - it's sort of like comparing the batting ability of Babe Ruth and Barry Bonds - both have unique relevance to their respective eras.
To be sure: some of Einstein's status derives from his status as a kind of cultural icon.
As important as Newton? Certainly not. Even Einstein would not agree. In fact, it's not enterely clear that Einstein is the most important physicist of the 20th century (you could make solid arguments for Dirac, Feynman, Fermi and Bethe, among others).
But his breakthrough was a big one, and he deserves to be ranked among the greats of science for it.