I too recommend TNG. If you get to the end of the series and you still want more, there's also Voyager, which is essentially the same as TNG and slightly more modern.

As a companion read to diving into (or back into) ST:TNG, I have to recommend what is still quite possibly the best pop-culture essay I've ever read: http://grantland.com/features/next-generation-turns-25/

I'm more a fan of the original. The moral lesson taught every TNG episode so bludgeoned the viewer I tired of it and stopped watching.

I really enjoyed Deep Space 9, too. It's got a comedic twist, and I just can't get enough of Quark and the other Ferengi. The Grand Nagus Zek, whose mellifluous voice I was sure I'd heard somewhere before, turns out to be played by Wallace Shawn, the "inconceivable" guy from the Princess Bride.

https://www.youtube.com/watch?v=SG_A0IOCfdM

One of the important ongoing themes is the relationship between Commander Sisko and his son Jake, which this article is about:

Deep Space Nine Is TV’s Most Revolutionary Depiction of Black Fatherhood

http://www.vulture.com/2018/01/deep-space-nine-revolutionary...

Here's an interesting interview with Avery Brooks (Sisko) and Rene Auberjonois (Odo):

https://www.youtube.com/watch?v=DnWmATqfebQ