While I am sure that many of you are reading James Maliszewski's outstanding column, Grognardia, for those who aren't, I steer you towards the "Old School" does not equal "Rules Light" post. For someone who has played more systems than Afghanistan has AKs, it's interesting to see people look under the hood of RPGs and start to examine why we like the games we like.
Alexander Macris from The Escapist Magazine, puts forth a very interesting way of look at things:
Perhaps my law school background has colored my thinking on this matter, but I don't view games as "rules light" or "rules heavy". I view them as "common law" or "statutory".
A "common law" game is one in which only the basic principles are given, and then it is up to the GM to elaborate those principles into the law of his campaign over time. However, a good GM does not run such a game by whim; he acts like a judge, following his own past precedents. Over time, the game ceases being rules light, because it has accumulated a campaign's worth of rulings, house rules, and interpretations.
In contrast, a "statutory game" is one in which all facets of gameplay are spelled out by the game designers. Questions that arise during gameplay are solved by re-reading the text and determining what they say, and ambiguities are resolved by trying to understand the intent of the writers.
The benefits of common law games are that they end up being customized to the experiences of their particular set of players. But they rely on having a good Judge (in the literal sense of the world) to issue good rulings, and keep track of his "case law". A bad Judge can screw things up with bad rulings, unbalanced decisions, and so on.
The benefit of statutory games is that you are not reliant on the rulings of a Judge. The drawback is that the games are more complex to understand up front, and may have just as many problems as a common law game, but be harder to fix.
This is, in writing, what a lot of people who have been gaming for years have experienced in the different games we've played. How many 20+ year vets can look back to how we played our D&D and say that we did it the same? I'm sure that if you plopped five old-timers down at a table and talked about the house rules and on-the-fly calls we or our DMs have made, we'd be there for hours. Hopefully beer is involved.
I don't see many "common law" games coming out these days, none of them from the major publishers. It's better business sense for a company to follow a "statutory law" mindset. Let's take the grand poobah of games these days, D&D4e, as an example. With the extraordinary number of powers and classes and feats and paragon paths and epic destinies and magic items, you've already got a million choices, but they are choices that are already made for you. "Oh? You want to play a double-scimitar wielding dark elf who isn't evil? Cool, choose this, this, and THIS."*
The more statutory you become as a system, the less you can rely on GM/Player caveat to break the mold. In Warhammer Fantasy's first two editions**, you are reliant on either shoehorning unique character concepts into the existing careers or creating your own. In D&D 4e, you need to support these options through, at best, creation of a new epic destiny or paragon path. At worst, you are creating 30 levels worth of powers, that may or may not unbalance the game.
I guess what it comes down to is some systems are better for some players. When you want your players to have the widest berth, able to do all things with greatness, a common law game is probably your best bet. When you want something a bit more realistic, where your characters are good at what they're good at and okay at other things, a statutory game is more the speed.
I like them all. I just like gaming.
* For the record, I LOVED The Crystal Shard when it came out, but I have really developed a loathing for Drizzt in the years hence. In particular, it was the spawning of "I'm the noble <insert heretofore evil race>, why am I persecuted so?" archetypes in games.
** I bought the three-ton box that is WHFRP 3e, and I tried to wrap my head around it, but I haven't. Maybe in November.