Evolution
Anyone remember "Evolution"? A very similar, but much superior movie. The plot is really almost identical. But without Will Farrell, the earlier movie actually WORKS. And if "Land Of The Lost" wasn't so disastrously cast, it might have worked as well.
Will Farrell is a CHARACTER ACTOR, people. This movie needed a somewhat funny, romantic lead. Someone who wouldn't just throw a bunch of slapstick around and pretend it was acting. The situation was funny; the lead actor didn't need to be such an overt "comedian", he just needed to react believably to the situations.
They cast David Duchovny as the male lead in "Evolution" and he was just right. Handsome, funny, believable. And Seann William Scott as his sidekick was perfect. The schlub they had playing Will Farrell's sidekick in this thing was a one-note joke.
Ryan Reynolds in "Land Of The Lost"? Golden.
Will Farrell in "Land Of The Lost"? Disaster.