Throughout the history of comic books, there has always been one recurring theme regardless of the era, or even the property. Whether Marvel or DC, Dark Horse or any other, comic books have generally always operated around the idea of good vs evil. A hero against a villain.
The likes of Captain America, the epitome of all that is good and right, and Superman, the embodiment of hope, perfectly capture this idea of the virtuous at one side of the spectrum, against the likes of Red Skull and Lex Luthor at the opposite side - however not all heroes are that cut and dry. There are certainly exceptions to this rule.
There are many heroes throughout the pages of comics that, although classed as heroes, were never designed to be liked. Some started life as villains, while others' loyalties were far more ambiguous, and some were certainly super heroes, just with wildly unlikeable personalities.
In some cases, in spite of such characters being created as far from virtuous, fans have ignored such intentions and found a way to love them anyway. This highlights how wonderfully interpretive comic books can be, as fans have even found ways to disagree with creators over the very characters they created.
Today, Wolverine can class himself among some of the most popular heroes Marvel have to offer, and is certainly one of the greatest X-Men of all time. Even before Hugh Jackman's historic portrayal of the character, Logan became incredibly popular thanks to his unique powers, and unblinking, badass attitude.
However, this certainly wasn't the case when he was introduced in 1974, neither was it the writers' intention. The character started life as a one off adversary of the Incredible Hulk, with the mutant brought in to track the Avenger for the Canadian government.
At the time, there was no intention of taking Wolverine's story any further beyond a mysterious superhuman working against the established character of the Hulk. Even after the writers decided that there was a story to be told, and brought the character into the X-Men, he did little to help his own cause, bringing tension to the team with his feelings for Jean Grey.
The character was almost dropped completely, but was ultimately saved when John Byrne took over the property in the late 1970's. Just several years later, thanks to the character's surge in popularity, Wolverine was given his own solo series, and went from strength to strength from there.