Encounter at Farpoint
"Are you certain you want a full disclosure of human ugliness?"
Not just a solid pilot, but also the perfect episode to begin this list; not because it's the first episode, but because the point of the whole episode was, essentially, "In order to truly judge or understand something, you have to be willing to really look beneath the surface." Literally. The answer to the mystery at Farpoint Station (and the salvation for the crew of the Enterprise D) was hidden beneath the surface. And, likewise, hidden among the bad episodes of season one, there are great ones. Like "Farpoint," which not only introduced our crew, but also gave us Q, who served as the show's most consistently fun and interesting villain.