Author Jon Krakauer focuses on the similarities between Chris McCandless and Gene Rosellinni in chapter 8. The two men are similar in a variety of ways. 

Both McCandless and Rosellini came from wealthy, privileged families. Both men also received college degrees and maintained high grade point averages. Both men, by all accounts, were also well liked by people around them.  

His real name was Gene Rosellini. He was the eldest stepson of Victor Rosellini, a wealthy Seattle restaurateur, and cousin of Albert Rosellini, the immensely popular governor of Washington State from 1957 to 1965. As a young man Gene had been a good athlete and a brilliant student. He read obsessively, practiced yoga, became expert at the martial arts. He sustained a perfect 4.0 grade-point average through high school and college.

Both McCandless and Rosellini went out "into the wild" sections of Alaska in search of solitude and perhaps answers.  

The major difference between Chris and Gene is in their motivation to seek out adventure and solitude in Alaska.  McCandless seems to be searching for some kind of spiritual peace. Rosellini, on the other hand, went out to the Alaskan wilderness in order to test a theory of his.  

He wondered whether humans could live as our forebears had when mammoths and saber-toothed tigers roamed the land or whether our species had moved too far from its roots to survive without gunpowder, steel, and other artifacts of civilization. With the obsessive attention to detail that characterized his brand of dogged genius, Rosellini purged his life of all but the most primitive tools, which he fashioned from native materials with his own hands.

Rosellini worked at his life purging theory for 30 years, and came to the conclusion that it is not possible for humans to live completely off of the land.

 I learned that it is not possible for human beings as we know them to live off the land.

Perhaps because of his failure, Rosellini committed suicide by stabbing himself with a knife. That is also a major difference between him and McCandless. McCandless died of natural causes after succumbing to starvation.   

Both men came from financially secure positions and both turned their back on those positions and on society in order to go in search of a connection with nature.  They both were filled with a belief in their ability to succeed "in the wild".  However, Rosellini wanted to try to prove he could live independently, without modern resources.  Mccandless wanted to have physical, mental and spiritual growth as a result of a communion with nature.  Also, Rosellini died as a result of suicide, presumable from the failure of his dreams.  Mccandless died as a result of injury and extreme weather conditions.