I just had the sudden urge to play this game, so I just picked it up from the nearest vid store.
What types of parks have you created?
I made one where the people were inside with all the dino's ouside. Didn't work too well, as the tourists were afraid of the small herbivores (forgot their names) running around my park, and the large gap in the fence where I ran out of them. I had to place turrets in order to keep the nasties out of my "peaceful" park.