Eric - getting closer
I honestly don't think that Ueshiba was the "greatest" martial artist of the 20th century. I know of one individual who defeated him soundly, when, allegedly, he was at the top of his game. (no, no, no, I'm not going in to this further, for reasons of confidences given).
But he was more than special. Let's say, for the sake of discussion, that Horikawa Kodo, was at least his equal in physical aiki and martial arts in general (don't know if that's true, in either direction, but bear with me). Horikawa was a fine gentleman - a school principal, and left a tidy legacy, so to speak, with one or two really excellent successors. But Ueshiba was a mover-and-shaker in Japanese society, and his manifestation of aiki/aikido transformed the lives of millions.
Ueshiba can do more than "inspire" us. I firmly believe that those who a) get good instruction b) put in the requisite 10,000's of hours can equal or surpass his physical abilities in aiki. It is a more complex question if we are actually following his path - I've outlined in HIPS how labyrinthine a path that might be. Further, can we achieve the level of greatness (with all the darkside that accompanies it, for he was not a pure soul, by any stretch), that he did? In other words, beyond aiki skills, what human being are we?
But without aiki skills, what kind of aikidoka are we?