Silva are you seriously saying the figure on the left is "cartoony"? I don't know what the one on the right is from but the left one is just a normal character with funky haircut.
Not just the hair, his body is too horizontal, almost like an oversized dwarf. It IS stylized to some degree and not trying to be purely naturalistic IMO. I think games like SWAT 2 or Commandos went for more naturalistic gfx, for eg.
I don't know what "body is too horizontal" means but UFO came in 1994, back then characters in videogames werem't necessarily cartoony, they just comprised of a handful of pixel that's all. Even hyper-realistic simulations of police procedures had characters like this:
These are kindda stylized not because Police Quest is a cartoony game but because fotorealistic graphics wasn't possible back then. The vibe, the writing, the general feel of the game had nothing to do with cartoony.
On the other hand something like Day of the Tenctacle was very clearly cartoony. The characters weren't fotorealistic either but they were intentoinaly goofy, plus the sounds, the music, the writing, everything was designed to be over the top to a very hilarious effect.
Nothing about the actual game of UFO is cartoony. There's nothing bright or cheery or bubbly about it. The sounds, music, lighting, writing, terror missions where technologically superior aliens are brutally massacring civilians...all that is intended to produce a feeling of doom and despair.
That's why it always pisses me off when idiots who never actually played these games just google a few screenshots and parade it on the interwebz as a proof of UFO being cartoony.