George and Myrtle Wilson are both tragic characters. Their tragedy arises from their circumstances. They are poor in a material sense and come from impoverished backgrounds. Myrtle and George both aspire to better lives and use different methods to realize their dreams. Myrtle has a clandestine affair with the super-wealthy Tom Buchanan, imagining that this will improve her circumstances. This dream is, however, a futile one, for Tom will never leave Daisy for Myrtle. Myrtle is just a fling, someone that he can use to boost his ego.
In a similar manner, George dreams of a better life which he believes can be attained through hard work (he is a dreamer/idealist). It is unfortunate, though, that he does not possess the resources to attain this dream. He has some kind of a relationship with Tom and sees this as beneficial. Tom, however, messes around with him and essentially makes a fool of him, first by having an affair with his wife and then by never keeping his promise to sell his car to George. He also misinforms the grey and dull George about who was responsible for his vivacious wife's death.
The connection George and Myrtle have with Tom Buchanan is what eventually leads to their doom. Myrtle is tragically killed in an accident (from a car driven by Daisy) when she runs out into the road thinking it is Tom driving towards their garage. George, in seeking revenge for her death (he is vengeful), kills Gatsby and then commits suicide.
One could also say that both characters are naïve, since they both believe that Tom Buchanan is the answer to their difficulty, without realizing that Tom is self-centered and does not care one bit about them.
Furthermore, George is timid and weak - he does not stand up for himself and is abused by both his wife and Tom. When he does take action, it is too late for the damage has already been done. Myrtle is both voluptuous and promiscuous. She flirts with Tom and has a sexual affair with him. She is also remorseless and materialistic. She feels no guilt for having an affair and seeks material wealth by having an affair with Tom.
Myrtle Wilson is very materialistic. She is unsatisfied with her husband's small repair shop and doesn't like her life as the wife of a mechanic. She is incredibly selfish and self-centered as is evidenced by her affair with Tom.
George Wilson is a more meek man. He seems to be content with his life...that is until he discovers that his wife is cheating on him. In taking the ending of the novel into consideration, one could say that George is passive-aggressive; he lets everyone walk all over him (Myrtle, in particular) and then, when he can't take anymore, lashes out in with intense rage and anger.
If you need one adjective that is suitable for both characters, both Myrtle and George are oblivious. Myrtle seems oblivious to the reality that Tom would never leave Daisy to be with her. Additonally, Wilson is oblivious because he fails to notice that Myrtle is unhappy in their relationship, and she is cheating on him. Of course, the realization of his obliviousness finally takes its' toll at the end of the novel.