Star Trek is weird... everybody loves the first two series, then everybody disagrees about which one broke the franchise.
I thought DS9 was very decent, if you phase out the whole wraith-plot even quite good, with a few brilliant episodes here and there.
I found enterprise to be a lot better than I'd expected after all the criticism it received. Not great, but mostly watchable. It had an uncomfortable feeling of constantly being ready to jump the shark, and sometimes even taking the leap, but somehow it always found back to its core and to being decent again.
It's Voyager that I consider the absolute low of the franchise. Bland characters, way too many plots that only revolve around nonsensical technobabble, and the frankly blatant (and apparently successful) attempt to save the show with boobs.
And now there's discovery, and I'm not yet quite sure what to make of it... The whole spore drive thing is ridiculously contrieved for no good reason, I'm not sure why another Klingon redesign was neccessary, and getting them stuck in the evil parallel universe was just about the bloody most stupid thing they could have done. I'm kinda enjoying it for now as a generic scifi show, but I'm not getting any star trek vibes at all from it.