Both produced absolutely incredible fantasy/scifi trilogies with groundbreaking visuals created by in camera effects, location filming, and truly innovative computer generated or assisted visual effects.

Following this success, they each decided to revisit their respective stories (obviously Jackson didn't write his) by making a prequel trilogy to their original trilogy, with the central plot points already known. (the weakness of prequels is another topic altogether) In the process of doing so, they largely abandon location filming and in camera effects in favor of green screen on stages. Characters that were previously real actors in physical costumes or puppets are largely replaced by CGI.

The ultimate result is commercially successful films that nonetheless left a void for many fans disappointed in the quality of the films compared with the original trilogies. Visually and in terms of story. Without being able to cite specific numbers, it is my understanding that both directors had access to much larger budgets relative to their original trilogies, yet seemingly accomplished less with them.

Just my take, but the similarity between Jackson and Lucas and their involvement with Star Wars and LOTR seem like mirrors of each other in so many ways.

Anecdotal, but it revisits the discussion of a lack of resources actually producing better creative outcomes sometimes.

Despite all of this, I respect both for their original trilogies and am glad we have them.