Alien and Aliens had them take a few pushes, Alien 3 was instant for Ripley, rez was a lengthy period but without any ribcracking until Wren got killed. AVP at least managed to make them seem like a struggle to burst out, even if the end result was pretty bad.
The kid shouldn't have been alive given the size of the chestburster versus his chest cavity size. His lung should have been crushed.