The Nagus (OB 21 March, 1993) score: 6

In seven seasons and 150 episodes, a soft story will sometimes make it to the soundstage, where the cast and crew must sell it.  "The Nagus" lacks dramatic tension, but earns distinction by introducing Grand Nagus Zek (Wallace Shawn), perhaps Trek's most amusing recurring character, along with The Rules of Acquisition and Zek's catchphrase, "You've failed miserably!"  Note the Godfather homage, with a satiric twist: acting-Nagus Quark forgets about respect at the mere mention of profit.

"When in doubt, be ruthless." - Zek 

TNG's Ferengi were cartoonish villains (they'd have twisted their  mustaches, if they'd had mustaches); DS9 surrendered to common sense, making the lobed ones comic.  Rom lags, still fretfully malicious here.  He almost spaces Quark, and seems (nearly) capable of doing so.

A parallel subplot, trouble in the Jake/Nog friendship, includes a scene that's bittersweet in retrospect: Ben Sisko reminding his son human-Ferengi relations are problematic.  Despite the knowing parody of capitalism, these Ferengi are alien in having a culture and ethos based on selfishness.  (It's the job of the "Nagus" to "negate 'us.'")
Alas, cultural cobblestones were paved by Hollywood P.C., as DS9's Ferengi became more courageous while accepting gender equality.  Admittedly, "Zek" might imply a cultural dead-end, thus the need for reform.
** The problem with a Ferengi conference is keeping the characters straight: P.C. or no, they all look alike. **