The Asgard actually died off as a race. They won the war against the replicators in Atlantis but the problem with the Asgard are their home planet diminished and something with their reproduction stalled. It's fuzzy but that's the gist.
Universe was canned because it was way too dark and they took out the comedy of the show that everybody liked. There was too much backstabbing, too many subplots, and the main cast wasn't very likeable. They lost a lot of viewers because of the direction they took and so it was canceled before even finishing Season 2.
Well SG1, Atlantis, and Universe are all canon and the movies after the first Stargate are I guess you could call spinoffs. I'm not sure about the animated series as I didn't watch it. Unlike Spiderman, Batman and all the continuous shows/movies these 3 series continued the story of what was happening to Earth, the "original" people, and how they were progressing.
Well that just sucks hard, I loved the race of the Asgard simply because it was exciting to see how much technology they had and the endless possibility's. What season did it finish at do you know.