I'm torn. I grew up on reruns of the original and new eps of TNG. Those two series will always be "classic Trek" to me. However, the others were all good in their own ways:
DS9's religious element was interesting, and it was nice to see TNG's tensions with Cardassia actually go somewhere. I also liked how setting the series around Bajor let them show off the darker side of the Trek universe, with the second in command being a former terrorist (against an evil, oppressive regime, but still), and having a holocaust/Japanese occupation of China type background between Cardassia and Bajor. Plus, DS9 really did for the Ferenghi what TNG did for the Klingons.
As a lady trek fan, Voyager's strong female crew was nice to see. The captain (Janeway), the chief engineer (Be'lana), the eventual defacto chief science officer (Seven of Nine), all were nice, strong characters. Even the villainous Seska was a strong character in her own right. I also liked how the Chakotay and Paris characters stemmed off from TNG. The actor who played Tom Paris also played Cadet Lacarno in the TNG episode with Wesley's court martial. Having him come back as Paris really worked for me. I also thought Chakotay was a tie-in to the native-peoples episode of TNG.
However, I have to be the outlier here and say that my favorite era is the Captain Archer Enterprise era. Era, not series. Trek has always been very clean, and I liked seeing the world get its hands dirty with grappling cables instead of tractor beams, a reliance on shuttles because people don't fully trust transporters, and a captain who brings his dog with him on the voyage. I also think T'pol is a nice, strong female character, and Hoshi is very competent and inquisitive, as one would expect from an explorer. I do think they screwed the pooch with the temporal cold war thing, but the Xindi storyline (if separated from the TCW) is quite good. I thought it was awesome to actually see the ship contain a compliment of special ops soldiers. I will say that I love what they did with the Andorian-Vulcan conflict, the episode with the 3-gendered race, the episode where Trip got pregnant, the episode with the hallucinogenic pollen, and I always enjoyed the Dr. Phlox character.