-Before Lord of the Rings Jackson Had:
Bad Taste
Meet the Feebles
Dead Alive
Heavenly Creatures
Forgotten Silver (TV Movie)
The Frighteners

-Before Star Wars George Lucas Had:
THX 1138
American Graffiti

-Both spent four years in the making of Star Wars and Lord of the Ring, respectively.

-George Lucas conceives and produces Raiders of the Lost Ark, an adventure serial.

-Peter Jackson directs a remake of King Kong, the original adventure serial.

-Peter Jackson directs The Lovely Bones, a special effects-infused mess that sucks all life out of its source material.

-George Lucas produces Howard the Duck, whose uneven tone and lifeless performances suck all life out of its source material.

-16 years after his original trilogy, George Lucas directs the atrocious Star Wars prequels.

-9 years after his original trilogy, Peter Jackson directs the atrocious Hobbit prequels.

-George Lucas retires from film-making in disgrace.

-Peter Jackson directs Tintin sequel in disgrace.

George Lucas at least had the wonderful American Graffiti to his credit,
and Raiders of the Lost Ark was a lot of fun.

Jackson never made anything that he didn't spoil with his silly, self-indulgent CGI effects, and that includes such potentially decent material as Heavenly Creatures and The Lovely Bones. Forgotten Silver could have worked in the hands of someone with talent, but he was able to turn it into an uninspiring borefest.

King Kong was cartoonish nonsense.

Overall, despite his flaws, I think Peter Jackson is the better filmmaker .

Something I noticed when I was compiling this comparison is that Jackson is more of director in general than Lucas. Lucas basically gave up on directing after 1977.