Back to the Future Part III (1990)

  This is my favorite of the trilogy but I was having trouble articulating why until I realized that this puts the focus back on Doc.  Christopher Lloyd is THE reason to watch this and he gets way more screen time in this, as opposed to Part II, and even more than Part I.  

After receiving a letter telling him that Doc Brown (Christopher Lloyd) was accidentally transported to 1885, Marty McFly (Michael J. Fox) is seemingly stuck.  He finds the Doc Brown of 1955 and convinces him to help repair the DeLorean that 1885 Doc helpfully buried in an abandoned mine.  The pair stumble across 1885 Doc's grave, with a death date only a few days after the letter was written.  Instead of returning to his original time of 1985, Marty decides to go back a century and save his friend.    

Not only does this rectify the previous film's mistake of Not Enough Doc Brown, it also provides him a love interest!  The (frankly, not terribly well-written but a step in the right direction, kind of a Manic Steampunk Dream Girl, if you will) schoolteacher Clara Clayton, played by Mary Steenburgen.  Their romance was way more compelling than Marty's terrifying constant brushes with incest or abandonment of the conveniently unconscious girlfriend.  

It wrapped up all the threads of Part II and provided a satisfying conclusion to the trilogy.  And so far, nobody has tried to remake, reboot, or reimagine it, thank God.