The Streets of San Francisco, as with most Quinn Martin series, is a standard crime drama. What makes the show better than most crime dramas is the father/son chemistry between Karl Malden as veteran Detective Lt. Mike Stone and Michael Douglas as the younger partner Inspector Steve Keller, the 70's, R&B-style theme music by Patrick Williams and the cool, pre-MTV opening credits.
What really made this show better than most is the fact that Quinn Martin did spend the extra money and filmed the show entirely in San Francisco. In the 70s, most prime time TV shows were filmed in Los Angeles. I believe Hawaii Five-O was one of only a few prime-time dramas from the early 70s that was filmed on location.
When Douglas left the series and Richard Hatch (from the original Battlestar Galactica, not the Richard Hatch from the first Survivor) replaced him, I quickly lost interest in the show. The chemistry between Malden and Douglas was very important to the show and Hatch had the thankless task of creating a character that in the long run was bland.
Despite the show's final season, I'm certain that if I had the TV on and heard the drum beats of The Streets of San Francisco theme, I am very sure that I will probably spend the rest of the hour watching the show.