most people can't draw the aliens design correctly so he might have just missed the mark.
it's the teeth and jaw. they're really small when you actually look at the head and compare size, the jaw barely has a chin, and the teeth only extend to the two big fangs, which are right at the angle of the maw, not actually further inside the mouth. but the most important factor is that most people outright refuse to give them lips either because it doesn't look as monstruous.
the excess of reflections make them look way fleshier and moist than they should too. some people can't stop themselves from showing off their photoshop skillz.
and the Giger Alien is based of the Hot Toys figure. i can tell immediately, the teeth are ingrown, the curve of the dome is goofy, and the line of the dome is way too high. it just looks fat and weird.
