wait a minute, wait a minute.......
-if anything ET is a ripoff of starwars-
i would just like to point out the depth of similarity here:
A Broken Family: Luke Skywalker wants to join the rebel forces but his uncle won't let him, and his father and mother were killed (albeit his father is now a cyborg out to destroy him)
Outcasts: Excluding the fact that Luke doesn't fit in at the rebel base or take well to his jedi training, the two droids (R2D2 and C3PO) are outcasts from Princess Lea's Ship.
Alien From Outer Space: Well there's Greedo, Bobba Fett, Jaba the Hut, Chewbaca, the Tusken Raiders (honestly the list of aliens could go on forever)
Villains Trying to Tear Them Apart: Darth Vader wants to kill Luke Skywalker and therefore take him away from his sister Leia. The Emporer wants to bring Luke to the dark side and tear him apart from his friends.
Moral of The Movie: "Nobody Gets Left Behind". We're all in this together and we need to work together to overcome big obstacles.
Honestly this is just one movie that could potentially fit into this mold that you've created for almost any sci-fi film. prior to Star Wars (1977) i believe Escape To Witch Mountain (1975) could feasibly fit this storyline as well. storywise, i believe it is very different from ET. it is its own movie and deserves a place as a classic disney animated feature.
things this movie had that ET didn't
-a main character who's parents had died and was dealing with their loss
-an evil killing machine alien
-a romance for an older sibling of the family
-an intergalactic space police council
-the hawaiian islands
-elvis
-two aliens chasing the escaped killer (one of whom was guilty of creating the thing itself)
-a member of the child protection agency inspecting the family for the upbringing of lilo
-and probably biggest of all....stitch crashed here to hide and ET hid here because he was left behind. totally different motivations for connecting with a child.
the list goes on, but in short: this film is not a ripoff of ET. ET isn't even about the relationship of the characters. Steven Spielberg said it was more the story about a boy growing up with divorced parents. ET does not go through an emotional change, Stitch goes full circle and changes immensely.

alright, i'm analyzing these films too much,but the point is similar as these stories may be, it's part of the genre. IT IS NOT A RIPOFF!!!!!!!!