Appealing to many people sounds like a good start and if the worst that people have to say about an episode is 'it was okay, at best' then no one's being pissed off.Define "good" Star Trek?
Many would put City on the Edge of Forever or Best of Both Worlds as good. I'd say they are ok, at best.
I would define good Star Trek as being Balance of Terror, Journey to Babel and The Trouble with Tribbles.
The Measure of a Man, Yesterday's Enterprise and Darmok.
Duet, The Way of the Warrior and The Siege of AR-558.
Deadlock, Scorpion and Timeless.
Twilight, Similitude and In a Mirror, Darkly.
What's Past is Prologue, If Memory Serves and Species Ten-C.
Calypso, The Escape Artist and The Trouble with Edward.
Remembrance, Nepenthe and Surrender.
Crisis Point, First First Contact and Reflections.
Kobayashi, Mindwalk and Ouroboros.
Tomorrow and Tomorrow and Tomorrow, Those Old Scientists and Under the Cloak of War.
Star Trek II: The Wrath of Khan, First Contact and Star Trek '09.
I don't think opinion is that wildly varied on what episodes people like, and 'good Trek episode' is not a particularly narrow target to hit either. The trick is to respect the show and characters, and tell a great story that would appeal to people watching the show.