Gintama is the best. My Gin-san deserves lots of fans! It is a series that, without doubt, captures almost every important essence of Anime (Comedy, Action, Drama, etc.) all within one show.
While it may be true that Gintama is mainly focused on the comedy aspect, the series is able to embody many action scenes, especially in the Arcs, as well as drama and sadness. This anime is the pure essence of entertainment. You will laugh, you will cry, you will become emotional invested in a variety of ways. Not having watched this anime is like missing out on a classic movie and that means that you haven't fully lived yet. *firm nod*