It's not Ben Hur but it doesn't have to be.

The answer is easy: Most people don't watch movies for artistic merrits (Stop fainting you cultured ones) we watch it to be entertained. This movie is entertaining, in fact if you are not a SCIFI fan you will find it even funnier.

The plot is classic, every American knows somebody who goves a little overborad with their fandom (on any subject.) We joke about the actors who are typecast so we know this movie almost before we see it.

The characters are great, and the performances wonderful. (This is the closest thing to a sympathetic role that Alan Rickman has ever had.) Sam Rockwell almost steals the show with some great lines:
"Didn't you even watch the show?"
They may seem harmless now but in a second the'll turn mean and they'll be thousands of em."
"I'm the crewman who always dies to show the problem is serious!"
Sigorney Weaver however has the best one, when confronted with something she has to do because it was on the show:

"Well I'm not doing it this episode was badly written."

You can't help but smile here. Even the actors must have been tickled by that. She is also a parody of herself in the big chace scene near the end as her front zipper gets lower and lower. It is unclear if it is a parody of that situation on every Sci-Fi series or if it's just to show her clevage which is still attractive at age 50.

In the end Tim Allen and crew of course as humans always do adapt and succeed. It's a fun journey, that actually reminds me of Gilligan's Island, (which of course gets a plug here.) it that its a story of Americans who can make it anywhere.

Its clean, its fun and will bring you up, buy it and watch it.