This is a fun, almost campy movie; don't try to think about it too hard. Rather, enjoy it for what it is.
It has an almost folklore-ish feel to it, as if what's being presented is more of a tongue-in-cheek tale (which it is fully aware of) and as such some aspects maaay have been exaggerated. And if you watch it in this vein, I think you will enjoy it quite a bit. But the second you start to take it seriously, it will crumble to pieces.
It's entertaining to watch. The characters are very large (and sometimes goofy/campy) and the plot heads in the correct direction most of the time.
This movie flew under the radar during its original release (not helped at all by being released 16 days before Aliens...) but had found extremely solid footing in home rentals/home video.
I remember my first viewing of this movie -- I knew nothing about it going in, I just sat there and watched it...and I loved it. It was funny, it was exciting, and in some few scenes even thrilling. It's not perfect, it has its flaws and blemishes certainly, but boy is it fun! :)