It depends on what you were hoping to get from it. Dr Who (and when I say this I should point out that I haven't watched every / most seasons since the creation of Dr Who) isn't really meant to be gritty sci-fi for adults, it's the sort of thing that gets shown at the same time as something like The Simpsons. It's a lot less serious than a lot of sci-fi.
Since the 2005 reboot there's been some absolute gems of episodes ('The Empty Child', parts 1 & 2, for example) and some absolutely terrible ones ('Victory of the Daleks', 'The Stolen Earth' parts 1 & 2, and the terrible ones outnumber the brilliant ones IMO by quite a stretch). The last 2-3 seasons of Dr Who were pretty mediocre as well.
I haven't ever got into Stargate SG:1. It seems like mediocre sci-fi that tries to take itself seriously but doesn't do anything interesting at all. Perhaps I've been unlucky in the 5-6 episodes I've watched, but there was one in there particularly that made me think "I'm not watching this again" because it tried to do something serious then the ending looked like it was written by a teenager rushing their creative writing homework, and I haven't looked back since, though I'm kind of tempted to find the episodes that have been listed on this thread as good ones and see where they take me.
IMO, the award for best sci-fi series to date goes to BSG (the 4-5 season series that started in 2004). Episodes didn't follow a 'generated script', the characters actually had character as well as character development, they weren't afraid to kill off established characters (and they didn't do dick-ish things like having the 'one episode ensign'). I also liked the fact that they didn't "tech the tech" (google the term if you're not aware of it). I think it also achieved character development which wasn't sci-fi driven but wasn't soapy either (ie. these are real people with real lives).
TNG used to be my favourite, there are some brilliant episodes of it, and as I grew up with it I'll always have a soft spot for it despite its many flaws. I've got seasons 3-7. My main problem with TNG is that most of the characters have no depth and very little development. The only two characters I can think of who couldn't be pretty completely described in less than two lines are Picard's and Worf's (and Worf's takes a distant second place to Picard's).
DS9 seemed like a soap in space, I didn't manage to get into it at all. Like SG1 I've watched say 5-6 episodes of DS9, though a few YouTube clips made me wonder whether I ought to give it another try.
ST: Voyager was just dull, dull, dull (though I watched a lot more Voyager than DS9), as was Enterprise. After Enterprise, I felt that they ought to put Star Trek into cold storage until someone with some vision and some original ideas was ready to take the helm.
I've watched some others like Andromeda or Farscape (did I watch the whole pilot for B5?), but I didn't ever seriously get into them.
Then why bother posting on a sci-fi series thread. It would be like my mother posting on this forum and saying "I don't think computers are interesting at all, you all ought to read a book or get some fresh air or something".