On the air from 1987 – 1994, Star Trek: The Next Generation was the second Star Trek series on the air, and can be credited with launching the modern franchise, creating the Trek canon as we now understand it, and starting an ongoing geek standoff (currently in its twenty-fourth year) about which captain was better, Kirk or Picard (answer: Sisko).
TNG continues the exploration of the galaxy begun by TOS while establishing the century after the Khitomer Accords as one of constantly increasing diplomatic complexity. TNG ushers in an era wherein Roddenberryan philosophy begins to break down as WW1 style webs of alliances promise to trigger enormous wars, and trigger them they do. The second half of TNG is rife with interstellar conflict. Picard represents the hotheaded idealism of Kirk tempered with the annoyed realism of Bones. With Data playing the Spock, TNG has the TOS triumvirate in 2 men. The primary theme of TNG is that behind the swashbuckling adventure of Kirk’s era must come diplomacy and maintenance. Picard doesn’t fly around and blow things up so much as he flies around oiling the federation’s diplomatic machinery so that other captains may fly around and blow things up.