Good point. It depends how you define "complete". Did the books tell 100% of the story, compared to the movies? Yes, obviously. But...in some areas...the books were written more like a history book than a novel. There is character development/understanding that is missing in the books. Some parts read like: "This happened. Then this happened. Then person x did this." Tolkien explained the motivations of the characters only at a high-level, but not in any great detail.
From the point of view of human drama and the personality of the CHARACTERS, the movies were better, but only because of the way Tolkien wrote. Story-wise, the books were better, obviously.
I'd say the Silmarillion definitely fits the idea of a "historical text", but I don't see how that applies to the Hobbit and LOTR themselves. They quite clearly present themselves as novels, complete with emotion and dialogue which would be foreign to a fictional historical text. I would honestly chock up that to the style of Tolkien rather than an intent on his part to portray these as "histories".
Scratching my Thomistic head on this one. 
How can an object/subject - the movies-, which has shown itself to be deficient in itself, provide a greater completion of the tale than the tale itself?
Adding or removing anything from the original text diminishes the essence of the Writer's created work. The text of LOTR, and subsequently all other texts written by Tolkien, ARE in esse THE Tale in its fullness, to whit the movies cannot add to the essence/being of The Tale; only mar or obfuscate.
A copy of the Jackson films should be placed on an Index, for historical purposes. Burn the rest!!!!!!!! 


And for Jackson himself......
(hee hee)
I'm interested to hear why you
loathe Jackson's adaptations, Kaz?

I know Christopher Tolkien hated them because they were action movies rather than an adventure, which I very much agree with. Is this what you disdain about them?