There once was a movie called "Stargate"
Then there was the spinoff TV show. "SG-1" is the name of a team of explorers who use the stargate. (There are several other teams, named SG-2, etc., which appear sometimes in the show.) Don't let the bad punctuation in the title put you off. It's every bit as good as Babylon 5.
I don't believe Xena has watched Bab5 either but you're right, both are very good shows. So was Farscape if you ever saw it.