I had a funny realization the other day.
When it comes to RPGs, I can't think of a single instance of any of the games I'm interested in being run with the original system.
For D&D-style fantasy, I use either Castles & Crusades or Fantasycraft (jury's still out on the latter--I broke down and bought the PDF and it looks awesome on preliminary skim-through, but I have yet to sit down and sink my teeth into it). But either way, I'm looking at some pretty serious modding involved any time I want to run D&D.
For Call of Cthulhu, I've recently decided on running games with Trail of Cthulhu, meaning my extensive collection of CoC material will have to be converted as I use it.
For Rifts, I'm using BRP of course. And, ironically, this includes Call of Cthulhu! Meaning the copy of CoC 6th Edition on my shelf is there for Rifts games...
It's kind of funny, especially when I think about the fact that for years I was a fairly pedantic gamer. I never really understood when people talked about "house rules" or making sweeping changes to published campaign settings. I think at any given time, I probably had one, maybe two, house rules in effect at most, and used settings pretty much as written.
I was never a rules lawyer or the type to say "you can't do that because it says so right here" and I flirted with talking about rules being "broken" but never really bought into that line of thinking. And now here I am, bashing rules and campaigns together like it's going out of style. I'm not entirely sure how that happened.
Partly it's having gotten plugged in to gaming blogs, for sure. There's such a fecund creative pool, it couldn't help but inspire me. I think another key element was my retrenchment into simpler systems, away from games like D&D 3.5 and GURPS and towards stuff like C&C and BRP. When you have a simpler foundation, it makes for a much easier jumping-off point.
(Oh, and I remembered there is one game that I play regularly that I use more or less as intended--Pendragon. It's just a perfect example of system facilitating game play. Of course, I still have a couple houserules for that as well...)