Nick realizes that Tom and Wilson actually have a great deal more in common than meets the eye. Although one is very rich and the other very poor, they are both being cheated on by their wives, and they are both unhappy as a result. Tom's wife, Daisy, is cheating on him with Jay Gatsby, of course, and Wilson's wife, Myrtle, is cheating on him with Tom. In addition, each of the two men seems to love his wife in his own way, even if their wives don't completely appreciate or understand or value that love. They each are just trying to make the best lives possible for their families, and they are both failing to make their wives happy. The only thing that really separates the two men and the things that they want is how much money each of them has.
George Wilson and Tom Buchanan are similiar because both of their wives are unfaithful to them. Their reactions to this information, however, are totally different.
George is stricken with grief and physically ill when he finds out Myrtle has had an affair. He locks her up and plans to move her far away in an attempt to physically separate her from her lover.
Tom becomes angry when he finds out Daisy is cheating on him with Gatsby, but he does not seem especially sad or shaken by the news. He remains fully in control of the situation and quickly manages to persuade Daisy that Gatsby isn't good enough for her. He is so confident that his wife will end her affair that he sends Gatsby and Daisy back to East Egg together, as if to flaunt his control over both. Unlike George, he doesn't feel any need to put physical distance between them; he knows that he has created a mental distance far superior.
Ultimately, George and Myrtle both die tragically, while Tom and Daisy stay married, though likely with the same unhappiness they had before.