Some say he's a comeedic relief. Others say he's a hero. To me, he's a deadbeat sugar addict who in spite of his traumatizing past, strives to be a good person with a clear, silver soul. Despite being 27 years old, he enjoys various childish activities like reading JUMP manga, eating parfaits, and lazing around on the couch while complaining about the current state of things (ex: not having a cool special move like a certain Bleach character). However, don't let his lazy and childish personality fool you, because he fought in a war 10 years ago and was feared by his enemies as the "White Yaksha". Nowadays, he struggles to pay rent and runs around with a giant dog, an alien girl and a pair of glasses.
Gintoki's past is mostly shrouded in mystery. It is unknown what happened to his parents, though he offhandedly mentions that he never knew his mother, implying that something may have had happened to her after he was born. All we know is that he was an orphan who would rummage through the corpses of fallen soldiers on the battlefield in hopes of finding food, which caused him to earn the nickname "Corpse Eating Demon" from nearby villagers. His life changed for the best, however, on one fateful day where he met Yoshida Shouyou, a kind and gentle teacher who became something akin to a father-figure for the young Gintoki. For the next couple of years, he spent his days at a temple school alongside Takasugi Shinsuke and Katsura Kotarou, laughing and arguing like an ordinary young boy.
It didn't last.
After getting dragged into a war and failing to save his beloved teacher, he eventually found himself in a graveyard, starving and waiting for death. That is, until, he encountered an elderly woman named Otose who was visiting her husband's grave. After being given the dango meant as an offering for Otose's husband, Gintoki promised to protect her no matter what. Some time later, he encountered an awkward boy being harassed at his workplace and an alien working for a gang, unaware that these two would become a part of his soul.
I'll be honest; I did not like Gintoki at first.
I thought he was a huge jerk with how he treated people. I kept wondering what my friends, who were really into Gintama at the time, saw in him. I assumed that I would simply go through the series constantly gushing over Hijikata the hot policeman and not really acknowledge Gintoki's existence unless I am forced to. That did NOT happen at all (I did end up crushing hardcore on Hijikata tho).
I think my opinion of him changed when I watched episode 27. Gintoki, who was known for being a bit of an ass, shows a surprisingly compassionate side when interacting with orphans (he even plays with a baby). When the orphans lose their father figure to an assassin part of an illegal fighting ring, they beg Gintoki to help them by offering them their "treasures" (basically a bunch of toys and stickers). Despite knowing that he may be walking to his death by helping these children, he still accepts it anyway because it would kill his soul if he were to reject their pleas. The episode really demonstrated his selfless personality and ideals, which continued to shine throughout the series. Though he has experienced so much pain (both physical, psychological and emotional) he strives to keep his soul a beautiful and clean silver color no matter what.
Plus I think he's pretty dumb and hot, and I want to pamper him with sweets and kisses, he's such a cutie.