what are the differences and similarities between Gatsby and Mr. Wilson?

One major difference between the two men is money. Gatsby has lots of it; George Wilson—not so much. George is just an ordinary small businessman, operating a none-too-successful garage in the Valley of Ashes. He has blonde hair like Gatsby, but he doesn't possess any of the great man's charm or charisma. When we're first introduced to him, it only takes a few words to describe him:

He was a blonde, spiritless man, anaemic, and faintly handsome. When he saw us a damp gleam of hope sprang into his light blue eyes.

But, at least, George has a certain rugged honesty about him. He may not be successful, but he's worked hard for every last penny. Gatsby's enormous wealth, on the other hand, has been made off the proceeds of various criminal enterprises.
What ultimately unites the two men, however, is that they are both destroyed by the American Dream. George is arguably the only truly grounded character in the book; he also is the only one who appears to believe in God. But he represents the forgotten class of the Jazz Age, the silent majority who simply put their heads down and worked hard while the East and West Eggers of this world carried on with wild parties, affairs, and riotous living.
For different reasons, neither George Wilson nor Gatsby truly belong to the Eggers' charmed world of wealth and opulence. Nor for that matter does Myrtle, and it's telling that all three of these characters die, with no one taking ultimate responsibility for their deaths. (George would appear to be in an impaired mental state when he kills Gatsby.) In that sense, George and Gatsby (and Myrtle, for that matter) are victims of the prevailing social system and its warped values, their tragic fates symbolizing the recklessness and heedless pursuit of wealth and status marking this period of American history, whose myriad casualties remain all but forgotten.