So, pretty much like every Star Trek series. TNG has a lackluster 1st season, an improved 2nd Season and finally becomes the show it is usually remembered as being in the 3rd. Enterprise has a rough 1st season but by the latter half of Season 2, it becomes much better and keeps trending upwards in quality.
Aside from the original series which is kind of stays the same in tone and quality from beginning to end, most Trek series have growing pains. The only other series I can't say much on is Voyager having watched very little of it. Even with Voyager, from people that do like it, they seem to point towards the middle of the series like seasons 3-5 as being really good. Voyager did seem to improve a bit when 7 of 9 joined the cast from the various episodes I've seen even though I didn't like the direction they were taking the Borg back then.
To DS9's credit, even though some of the crew is bland still and could be replaced by a talking paperweight (which would suddenly make that character more interesting), there are a couple other members that I do like and have warmed up to and while I'd like to see the writing a little bit tighter and smarter, for the most part, the episodes I've been watching have been interesting enough to keep plowing through at a regular rate which is something Voyager couldn't get me to do.
Season 2 from the beginning shows signs of improvement over Season 1 when they have a 3 episode story arc occur over its first 3 episodes. You can tell the show is beginning to realize some of the potential it has and how it can be different than the Trek that came before it by staying in a more stationary place which is getting more into the political elements of the part of space where it is patrolling. One particular highlight has been the Cardassian tailor on the ship. Both of his episodes so far have been one of the top episodes in each season I'd say. He helps make Dr. Bashir a more fun character to boot. So, even if I'm not at the "good stuff" yet, there are still other elements and things in place to keep me watching the show right now to find it pleasant enough without it being a struggle as I wait for it to truly gel.
As far as the crew goes, I think Kira Nirese(? not sure on spelling) is probably my favorite character right now. Following her would be Quark and Odo. One thing I didn't expect to like was a Ferengi crew member since their other Trek appearances never seemed to indicate much depth to their race plus their look is rather ridiculous but having a sort of criminal and profit seeking station resident has ended up being more entertaining than I thought. It helps with Odo playing the no nonsense lawman and straight man in their cops and robbers routine. It seems to me that the mystery of Odo's race is one the writers are setting up for a payoff down the road and I hope its worth it. After that, I'd probably rank Jake Sisco as the next best character though more for his partnerships with Nog. He hasn't really had much to do in the series so far or been involved in much either but I see him as a second crack at what the writers had wanted to do with Wesley Crusher on TNG and succeeding by not making him some kind of chosen one with Wesley and focusing more on what it would be like for a regular child in this envioronment.
Notice that the best characters so far are pretty much all non-Federation? As for the remaining members, I'd put Chief O'Brian next in line although sometimes he just feels like a Scotty 2.0. Then Dr. Bashir who I'm starting to warm up to a bit from a few recent episodes. Sisco and his odd facial expressions next. Finally, at the bottom, no-personality Dax.
Guess we'll see if the bottom 4 can change things as we progress but, in a positive spin, even though I'm a bit ambivalent towards the Starfleet members, at least I don't hate them or are annoyed by them like some of Voyager's crew. There's still plenty of time to find a way to make them interesting (like Bashir's spy games with the Cardassian tailor) find a way to better characterize them. Right now, I could kind of describe O'Brian and, I guess Bashir's personality and traits if I had to though I'm not sure how accurate the list would be. But I've got nothing on Sisco or Dax and how to write up their personality. With Sisco, I'd be relying a lot on the first episode still along with a bit of the 3 part arc to start S2. With Dax, it's more what others say about her than anything she has really shown. Still, while these characters may not be part of the draw in watching another episode or compel me to watch more of the series, they aren't pushing me away from the series either so they aren't harming anything. I'm just wishing and hoping they can become more than stay neutral. With TNG and Enterprise, I liked all the character so even when an episode focused on one particular member, it didn't take away from the enjoyment of the show unlike Voyager and "Oh no! It's a Chakotay episode! What did I do to deserve this?"