He has been credited with a quote that is usually stated as, "If you can't explain something to a six year old, you really don't understand it yourself." In terms more applicable to his field, one might say, "If you can't explain your theory to a layman, you don't understand it yourself."
Einstein's theories are quite complicated. The actual general relativity equation looks like this:
Naturally, most of us who do not hold doctorate degrees in physics do not understand this equation at all. But rather than leaving most of the world lost and confused, Einstein explained his theories to us in very simple terms that anyone with a basic knowledge of physics could understand, using his thought experiments (example). By simplifying his theory and using language and examples that were clear, he allowed people not only to grasp his ideas, but to also understand how solid the ideas were. It is very difficult to find fault with his theories; even the layman can agree that his thought experiments are reasonable, logical, and appear correct.
The contrast with the LDS method of teaching is striking to me. LDS doctrine contains several principles apparently so complex, that even a lifelong dedicated servant of the Master Teacher is unable to comprehend. For example, Gordon B. Hinckley admitted that he did not understand why God commanded that members with black skin be denied the blessings of the priesthood (source); the Church has not made clear why there is a discrepancy between DNA findings and the Book of Mormon, but have instead changed the official stance on the origins of Native Americans (2nd paragraph); leaders prefer to simply not talk about Joseph Smith's specific form of polygamy rather than attempt to explain it. The Doctrine and Covenants 19:22 even goes so far as to state that there are things we cannot know or we would "perish." We are assured that there are reasonable explanations for all of these (example), but that the answers are far too complicated for us to understand. Even the most spiritually advanced men on the planet do not have a grasp on the answers to some of these questions, or at least not enough that they will attempt to explain it.
Indulge me for a moment and compare Einstein with the LDS god. Imagine that Einstein wrote in his famous papers, "Something plus something else equals another thing when you calculate it with something else. I know what the somethings are, but the reader would not comprehend it, so just trust me on this." Suppose Einstein had not even attempted to explain the theory to his colleagues with whom he worked for years. Other scientists would say, "Well, the rest of the theory makes okay sense, but the problem is that it all depends on this original equation that you're not giving us! Can you be a little more specific? We're pretty bright and we've done everything we can to understand your theory." Einstein, if he were like the LDS god, would reply, "You are just not capable of understanding," or "If you knew, it would destroy you. In the meantime, just base all of your lives on the assumption that my theory is correct."
After a few years of this game, it would become pretty clear to a reasonable person that he didn't even understand what he was talking about, his theory wouldn't pan out, and he probably just made the whole thing up.
I do not hold a Ph.D. in physics, but I have a pretty good understanding of the theory of relativity. I don't hold a degree in biology, but I have a good grasp on evolutionary theory. Both seem like very solid theories to me. However, I was raised in the LDS church my whole life, served a 2 year mission, graduated from seminary, and served in several callings (including 2 Elders' Quorum Presidencies), and as hard as I have tried to understand polygamy, denial of priesthood to people of African descent, and the severe problems with the Book of Mormon, I am at a total loss.
If God cannot explain some of the most fundamental doctrines to even the highest ranking followers, then there's a good chance that He does not understand them either. That leaves me to believe that the entire LDS church is built upon a foundation of sand. And when the best way to make sense of God's doctrines is that they were made up by men, then there is apparently an enormous problem with God's one true church.
Call me faithless, but I will stick with things that make the slightest sense before accepting things no one understands.