There are some truly good episodes in TNG... One of my favorites is "the first duty" which apparently was at some point required viewing at the United States air Force academy.

Overall though I like ds9 better because it's a more "honest" look at humanity... But darkness aside there's kind of an optimistic broad character arc/thesis where the good guys each in their own way is on a journey overcoming impostor syndrome (sisko, Kira, odo, Bashir, ezri, Jake, quark, rom, garak, and nog all fit this model to some degree, and even damar when he becomes a good guy basically fits this model), and the bad guys all are brought down by their classical toxic leadership attributes (dukat, Winn, weyoun, FC, but also minors like admiral leyton).