I haven't wathced every episode of the Justice League, but I've seen my share. And I find Secret Origins to be a good start to the whole series. What better way to unite the greatest heroes in the world than a threat to the entire world.
Unfortunately, the movie seems to focus too much on Batman and Superman in the beginning (I know they're the frontmen of the league, but still). It would have been nice to see where GL, Hawk Girl and The Flash suddenly comes from.
Another thing keeps bugging me:
Why is The Flash so ridiculously silly? I remember reading a quote from one of the makers of the Justice League, saying that he is so fast, that he can have a bullet fired at him, run across town, get a bulletproof west and return, before the bullet hits him.
Why does he move so "slow" then? And why does he never seem to notice when danger approaches? How can the fastest man alive trip over something as simple as a mine? I realize that the directors has to solve the problem about him being too fast, but they haven't handled it very well in my opinion.
Other than that, it's a solid story and it introduces every hero and their abilities and their personalities very decently. Furthermore, it presents them with a valid reason to even form the League in the first place.
It's definately worth owning.
I'd just wish that Warner Brothers would stop releasing 3 episodes at a time and just give us a box with each season, as every fan of the JL seems to want them to do.