Like comparing Steve Harvey to Mr. Potato Head, this comparison isn't particularly new or original. People have been pointing it out for such a long time that sometimes, we think Danny DeVito plays up his resemblance to Mister Spaceley from 'The Jetsons' on purpose.
DeVito is a unique looking actor, but the combination of his height and his hairstyle make the resemblance unavoidable. If he didn't like it, he wouldn't routinely fashion his facial hair after Mister Spaceley, so we can only assume he's a 'Jetsons' fan.