The closest likeness would go to the Roswell 1/5 statue, because it is almost an exact replica of the original sculpt by giger which is now on display in gruyere...
However, the caveat is that it reflects the character sculpt made for production around bolaji's form, but does not reflect the final hero suit with suitmation wrinkles, actual colors, or the peeling skin-- it also lacks the movie accurate elbow spurs and paired fingers on gloves with wrist ribs
( kenner had these),
and there were flat horizontal elements at the very top of the trouser section, just beneath where the ribs overlap ( also as shown on the kenner sculpt which appears as random horizontal stripes around the midsection)....
also many dislike the static nature of the figure...it was after all a sculpt for a suit.
The medicom is pretty accurate, but small, rubber suited for the most part, and the mouth is a little off...the paint is unrealistic and also suffers from separated digits...though fairly accurate, not terribly impressive as a figure. It has the same narrow dome as the ss maquette, but also nice profile...
The ss maquette is great overall look, but has an incorrectly shaped dome around the face and cheeks ( though the profile looks decent) imprecise and inaccurate details throughout, and Dracula hands....is huge though and has interesting colors.
The only other I'd say is the cinemaquette, but it has an incorrect profile, ( the head is too tall) nice face and mouth, correct hands, but a pose many despise...though it was supposed to reflect the moment it spun around to attack Parker.
It has the correct "peeling skin" effect, not reflected on the Roswell, or most other representations.
Also the heel is not tall enough ... Kenner alien captured this detail beautifully.
Hot toys 1/6 is nice, but doesn't scream alien...the shape is all over the place, the head shape, profile, mouth, skull, interior, ...it's all inaccurate ...the details are precise, but they are grossly inaccurate...I loooove hot toys, but they really missed an opportunity to create something special....one of the few times medicom whips ht's butt...
The fingers appear as branches or flippers depending on which are attached.
The feet shape are wrong...should appear as a high heeled wedge almost with a flat sole...
The neca alien is pretty awesome, but I'd wait for the the next 1/4 scale for a new and hopefully DEFINITIVE alien figure