I went into this movie expecting crap, because it was made for TV, but I was pleasantly surprised. The acting was very good, with each actor seeming very comfortable in their characters. Treat Williams and Jeremy London worked very well as a uncle/nephew team, and Hugh Keays-Byrne delivered some serious laughs as Scottish gun smuggler-turned-guide McNiff. Bryan Brown portrays the film's antagonist with equal arrogance and intensity; very entertaining.
The problem is most people were expecting a good quality movie. The reality is, this was made for TV, and if you lower your expectations completely, it's actually a good movie.
The science is flawed, but so was Verne's, so no harm no foul. The special effects are bad, but like I said, it's made for TV. The scenery and locations are engaging and very cool. The caves are somewhat cheesy at times, but that's easily unnoticed if you pay attention to the characters. The action is visibly fake at times, especially the gunfire and fistfights, but not in a bad way.
All in all, the film contains very likable characters, genuine humor, and a very good soundtrack (another thing most reviews fail to mention). Just watch it in good humor and enjoy the story.