...all you do is basically collecting 18 dinosaur eggs as well as completing...
I thought it was 100 eggs...
But yeah, I played this a few times, and the time I came close to beating it (I left my SNES on for about 4 days) I couldn't figure out for the life of me how to drop the nerve gas (you just walk into the middle of the eggs... **grumble grumble**
The first couple of hours are fun (when you're goin around and have no idea what to do, and are just killing stuff), but after that it sucks
As for other terrible endings... I don't remember any outside of the NES/SNES era, since 90% of those ending in "Thank You for Playing + Credits"