The key difference is the quality of the story telling.

Both of the Hobbit films I've seen were narratively coherent and had fine acting performances and were actually rather well paced.

It had CGI in it but the story would be very difficult and probably prohibitively expensive to do with purely practical effects and for the most part the CGI is fine.

The PT had loads of fine practical effects, was terribly directed, terribly written, badly acted and hardly made any sense.

I really think the reason the Hobbit films aren't as big a deal as they might be is because the source material is now out of fashion (Wizards were very big in the noughties).

If these films had come out right after Return of the King they might have been just as big and nowhere near as drubbed by the critics. The corporate shenanigans that delayed these films ultimately hurt them.

In this regard it resembles the PT which ideally should have gone into production in the late eighties leading to an Episode 7 around 1997.

TPM was a crap movie but part of the horror of the piece is we waited expectantly for sixteen years, hearing rumor after rumor and eventually when the film came out even a good film would have had a hard time living up to that level of anticipation.

That it was awful on top of that just made it so much more of a let down.