Well, well, well. Seems like the creators of Stargate SG-1 weren't so dumb after all. I mean they may have cancelled the show, but they also created one of the best spin-offs I've ever seen. No comparison to stuff like CSI: Miami or CSI: New York, Law & Order: Special Victims Unit or Criminal Intent (well, seems like doin' a crime-spin-off isn't such a good idea after all).
Bueno, now you might ask, what's the difference between Atlantis and SG1. Of course I can answer your question.
First, Atlantis is in another galaxy. That's especially important as this means: no Goa'uld, no Ori; They fight the Wraith over there; some life-sucking aliens, which you can imagine like Michael Myers on morphine with some sort of saliva problem.
This also means: lots of Ancients and Ancient Technology. Nooooo, not elderly looking women and their walking frames, highly advanced civilisation and their highly advanced, way cool looking, highly buggy technology (Microsoft must have had their hands in this).
And yet another thing is: Energy problems. Somehow the highly advanced Ancients haven't thought of equipping their highly advanced, way cool looking, highly buggy technology from Microsoft with long lasting batteries. That means that the main characters of this series have to go out all the time and fetch some new energy source from the local ZPM store. Well, at least they got that one. Imagine them running around, only stumbling over these things by accident! Man, THAT would be hilarious.
So all in all, the series really is great. Well, sometimes you might miss good ol' General - pardon - Colonel Jack O'Neill, but he even has his cameo in an episode or two, so if you're a dement...err...devoted watcher such as I, you'll find him there two.
So all I can say as a conclusion: The show really is great. I love the characters, the stories are just as good as SG1's (maybe with a little bit less time-travel-stuff) and the special effects are in no way behind the latest/last SG1 episode.
So my recommendation: Watch SG1 and do watch Atlantis. They're both fantastic.