Considering myself a MAJOR Trek fan, the by far best episode of TNG is "The Best of Both Worlds" (both parts combined). The rest of the ten best (in no order):

"All Good Things"
"The Inner Light"
"Darmok"
"Q Who?"
"Chain of Command"
"The Measure of a Man"
"The First Duty"
"Yesterday's Enterprise"
"Sins of the Father"

My honorable mention episodes: "The Neutral Zone", "A Matter of Honor", "Sarek", "Unification" "The Drumhead", and that one where Data takes command of the other ships with that detection net that pisses off the Romulan Tasha Yar. That was a good one.

The worst episode ever is pretty much half of the first season, but the worst by far is the one where Yar has to fight that African woman with the poison gloves. That episode was boring. "Code of Honor".