There are some people who are comparing Stargate: Atlantis to Startrek Voyager. As a Trekker and a huge fan of Voyager, SG: Stlantis is not similar to Voyager. I have seen all the Voyager episodes, and so far, none of the episodes have had same storyline.
Although they both start off in an unknown location where they cannot return to earth, the story that continues after is completely different.
There are some similarities, such as the Wraith vs. the Borg and the Atlantians vs. Caretaker, many other things do not match.
Atlantis has a unique storyline, that is very fun to watch and will continue to make you watch it again and again. Also, since this is made by Sci-fi, there are no commercials!
However, if you are a Trekkies, where you want variety, you might not like the show. In the show, everyone speaks English (lol I know) and most of them (excluding the wraith) looks like human. Also, the technologies are not as techie as in Startrek.
Give it a chance. I'm sure many people will like it. Also it will keep continue to make you watch more. Although not as scientific as Startrek, this is a must for every startrek fans!