I assume with enough bullets of sufficient size, anything alive would go down eventually. It's hard to imagine an animal having fully bullet-proof skin. If they did, there's still the matter of absorbing all that momentum. You'd essentially be beating it to death at that point.
Since we're bringing up Jurassic Park, in the book, they deal with the island by sending in the military. Presumably, they shot the dinosaurs dead. I haven't read the sequel, so things might not have gone as well as one would hope, but it's presented as if this were going to be a solution.
I'd bet Michael Chrichton was a lot better informed than anyone here who isn't a legit career paleontologist. While that doesn't
necessarily
make him correct, it does at least constitute a compelling argument.
There's a difference between canon and not-stupid.