It's entertaining once, but impossible to watch a second time, as the novelty value has worn off and you can see just how bad it really is.

I truly think it has a cult following for its badness.
Hilarious to rip to shreds on a boozey night with friends.

Travolta elevates it from merely awful to hilariously awful. He's quite incredible.

It's not that funny really, it's not like The Room or Batman & Robin. It's just a dumb, plodding sci-fi film with cheap CGI. The only fun thing in it is Travolta's scenery chewing.
For something released by a big studio (Warner Bros) it's particularly poor, but it's probably no worse than most low budget direct-to-DVD sci-fi, action and horror movies.
Maybe it's more of a laugh if you watch it with friends + alcohol, watching it sober and alone, not so much.

It's a must see. It's definitely one of the worst as a big budget films, though, so brace yourself.
Are You Watching Closely?
You're an idiot

It's so bad is hilarious. Watch it as a comedy and you'll never regret it.