I really like Stargate: SG1. I watch it every week. The characters are good, the stories are good, and despite every planet looking a lot like the forests near Vancouver, the universe they play in is good.
I wasn't expecting much of Stargate Atlantis so it came as a pleasant surprise that it was so good. I mean really good. The jury is out on the characters but the story and backdrop are really outstanding. The bad guys have to be amongst the scariest bad guys I've seen on TV before. Think really really bad ass vampires. Vampires who defeated the ancients, which is particularly scary since the ancients are the ones who built the stargates in the first place!
So I can safely say that I recommend giving it a try. I think they have a hit on their hands.