u/Torlek1

TNG has 13 recycled plot episodes out of 176, 7.4% of its episode total.

10 of them were rehash stories from TOS. The others were recycled within the same TV show.

TNG 1-3 The Naked Now

From TOS 1-4 The Naked Time

TNG 1-4 Code of Honor

From TOS 2-1 Amok Time

TNG 1-5 The Last Outpost

From TOS 1-18 Arena

TNG 1-10 Hide and Q

From TOS 1-17 The Squire of Gothos

TNG 1-12 The Big Goodbye

From TOS 2-17 A Piece of the Action

TNG 1-18 Home Soil

From TOS 1-25 The Devil in the Dark

TNG 2-7 Unnatural Selection

From TOS 2-12 The Deadly Years

TNG 4-21 The Drumhead

From TOS 1-20 Court Martial

TNG 5-21 The Perfect Mate

From TOS 3-13 Elaan of Troyius

TNG 5-25 The Inner Light

From TOS 3-3 The Paradise Syndrome

In my opinion, early TNG could have done a bit better by ditching at least four TOS copycat episodes.

That includes Code of Honor, The Last Outpost, and Unnatural Selection.

Should these have been substituted with more Phase II scripts?

Over the course of the entire show, only two Phase II scripts were used.

These scripts have never been used in either Classic Trek or modern Trek:

Kitumba (two-part episode)

Cassandra

Practice in Waking

Deadlock

Savage Syndrome

Are Unheard Melodies Sweet?

Lord Bobby's Obsession

To Attain the All

The War to End All Wars