(I mentioned Pathfinder RPG a few posts back, but in case you missed it: it's a fantasy RPG mostly based on the open content of Dungeons & Dragons 3.5, with many tweaks. Some actually refer to it as version 3.75 of the d20 System.)
Yes, I do tend to prefer fairly light roleplaying game rule systems. But when I say 'light', I'm talking in terms of not being overly complicated, not necessarily in terms of mass. There is a certain pleasure in holding and browsing a well made rule book that non-gamers probably can't understand. It's not necessarily only about playing the games (and obviously you don't even need a rulebook in order to play a fun RPG). I have rulebooks I've never used, and frankly might very well never use. I don't regret buying a single one of them, though.
I don't really own a particularly huge library of RPG products, as I've never been one to gather lots of source books and other expansions. Like I said, I'm not keen on overly complicating things, and I prefer creating my own game worlds as well, so for most games the basic rules are all I need. And rule books cost money, too. But some of the books on my shelf are treasured possessions, invoking lots of nostalgia, like the aforementioned AD&D 2nd Edition, and West End Games' Star Wars RPG. Even if some games are replaced by newer equivalents (like Pathfinder might come to replace 2nd Edition), I'd never get rid of them.
Yes, I'm a hardened materialist, taking pleasure in owning beautiful things. So what?