Gintama is a historical/sci fi manga that takes place in the samurai time and aliens come to earth.
Story - It doesn't really have a story, just arcs and random comedies. Each episode/few episodes do have a story of their own, but there's not really a "main" story.
Art - 9/10 The art is clean and easy on the eye, although sometimes the male characters look too buff. xD
Sound - 9/10 Pretty nice, Madao music is awesome, same with Prince Hatas's theme.
Character - 10/10 The characters are interesting and have their own flaws and lovable points, but because there's no actual story, there's no character developement, but then again, I think Gintoki is fine the way he is.
Enjoyment - 10/10 It was beyond hilarious and has the most twisted and awkward/inappropriate humor that came from who knows where.
Overall - 9/10