Tolkien vs. Lewis

I took a nerd quiz a while back that asked what you think of the Lord Of The Rings trilogy and one of the answers was "You can't really understand them until you've read the Silmarillion." I couldn't choose that answer cuz I hadn't at the time. But now I know it's true and I still haven't even started the Silmarillion proper yet; I've just finished the opening chapters over the Valar and already large chunks of story have been cleared up. And there's also a letter in the preface that Tolkien had written to a colleague that ties everything together from start to finish and simplifies it all. Mind boggling. It's just made me think about the relationship between Tolkien and C.S. Lewis.
They were friends but not as close of friends in the end. I'm pretty sure that the main reason was that Lewis wasn't as hardcore into the Catholic catechism as Tolkien, but I just wonder sometimes if Tolkien wasn't a little jealous of Lewis' ability to simplify a concept. They both put religious overtones into their works without referencing any direct Christian teachings. Tolkien, in the above mentioned letter, said that he hated deliberate allegory as an explanation for the creation of this Middle Earth universe with its own mythology and rules. And that's cool, but when you step back and look at it all, (even though it's briliiant story telling and fantasy) it seems so unnecessarily complicated. He worked on it for years and left a lot of unfinished material on this world he created. Lewis was clear about the fact that he wasn't writing deliberate allegory either (with the exception of The Pilgrim's Regress) and yet none of his fantasy or science fiction was as much of an undertaking as the Middle Earth sagas. You can also glean as much of the moral implications from Lewis' sketches as you can from Tolkien's vast murals. Still, it's not a complaint... I wouldn't reread my Middle Earth stuff if I didn't love it. It's just an observation touched off by my initial reaction to the early chapters of the Silmarillion.