Cats have large, forward-facing eyes, and a relatively short snout and jaws (especially smaller cats like the domestic cats, caracals, etc). This makes them look less like a typical predator (long jaws, like wolf's) and less like a typical grazing animal (side-looking eyes, long jaws, like a horse or camel). They look close enough to humans to look cute, possibly triggering some if the low-level reactions which human babies trigger.

Arthropods and even snakes are morphologically too distant for that. Nevertheless, people usually find large-eyed geckos more cute than armor-eyed chameleons or tiny-eyed crocodiles.