@kagan My top ten original series episodes, in the order they come to mind:

The Doomsday Machine
The Ultimate Computer
The Menagerie
Court Martial
The Enterprise Incident (yay season 3 had one great episode!)
Amok Time
Arena
Balance of Terror
Errand of Mercy
The Trouble with Tribbles

Outside looking in:
City on the Edge of Forever (good ep; I am not as ga-ga over it as many are, and I have no opinion as to whether Ellison’s original script - which I have read - would have been better)
Mirror Mirror
Space Seed
Day of the Dove (hey, another S3 episode!)
(The Tholian Web is also good!)

I guess my favorite NextGen episode at this point would be “Q Who”. I wasn’t a fan of the show the first time around and it’s aged poorly.

@kagan I’m an unreconstructed original series fan. I think it has more good episodes than The Next Generation, and by a pretty wide margin. And its peak episodes blow NextGen’s out of the water.

TOS did finally get lapped in quality by Babylon 5, but B5 was arguably playing a somewhat different game, so the comparison may be unfair.

The only season of Trek I’ve seen which I think surpassed the first two of TOS is the first season of Picard.