The Emissary is my favorite pilot episode of a Star Trek series.
That doesn't really speak to the strength of The Emissary but more to the overall weakness of the pilot episodes. Caretaker is not bad, but it's relatively boring. Farpoint is just... gah. There's some good stuff in that episode, but god is it a pile of cornballs. I never really watched any Enterprise aside from a scattered few episodes so I can't judge that one.
As for the OS, I guess it depends on whether you consider The Cage or Where No Man Has Gone Before. The Cage is passably interesting. It has a neat, though very 1960's sci-fi premise, but that's it. WNMHGB is better, but it doesn't really feel at all like a pilot episode. Still, fairly good overall.
The Emissary does have a few problems with the writing and most of the acting is... awful, but, as a pilot, it set up quite a few plot threads successfully, introduced a rather eclectic (for Star Trek) cast of characters rather well and was a fairly interesting story overall. Not a great episode, but when I rewatch it I usually enjoy it, except part 2 is pretty tedious at points.
I'll give TNG the award for worst first season. There is not a single episode in the first season that I'd call necessary or worthwhile viewing. Maybe "Conspiracy" but that's because it's so batshit crazy and un-Trek-like. The rest? Seeing it once was enough.
TOS had "The Naked Time" which was far more fun than 95% of TNG's first season, so it wins on that only.