Lucas waiting two whole decades and not doing any credited directing in all of tnat time are two big strikes against the prequels that the Hobbit movies don't have. It helps that LotR was made after the digital vfx wave had really got going, so that even the cgi overload of The Hobbit doesn't seem too out of place by comparison. The RED cameras are a much closer match to the Super 35 of LotR than the sony 2/3" hd cameras are to the cinemascope of TPM and the OT. You can bet that if The Hobbit actually had gotten made pre-2009, they would've just shot it on film.

The comparison comes from doing the prequel (written first by Tolkien before he wrote LotR) after you've already told the "main" story on film. You suddenly feel the need to force all these connections to the originals. The irony is that the Star Wars prequels, titled episodes 1-3, feel so disconnected from the ones titled 4-6 while a movie of the Hobbit, which could've done its own thing, feels bolted to a movie titled Lord of the Rings.