Rules Light

Typified by a universal mechanic and no or only one or two subsystems.  Rules tend to be based around the GM making a judgement call, or wave your arms, scream, and toss dice.  Characters tend to be easily created in a minute or two, and only takes up a single side of a sheet of paper.  People can be explained the game and start GMing in about 10 minutes.  The books tend to be largely fluff.

Standard: Teenagers From Outer Space, Ghostbusters, Risus, BESM1e, Marvel Super Heroes Original Basic Set.

Star Wars d6 may be a good representation of the upper boundary.


Rules Medium

These types of games typically have a few subsystems.  They often have a unified mechanic, but minor subsystems may ignore this standard device.  Common adventuring activities tend to have explicit rules, but less common or mundane things are often left to GM judgement calls.  Characters tend to take a single piece of paper, but may flow to the back side.  These characters usually are fairly quick to create, maybe about 30 minutes or so.  People can be explained enough of the game to play in 15 minutes or less, but learning to GM may take an hour or two.  Books are equally mixed with hard rule data and fluff.

Marvel Super Heroes Advanced Set may be a good representation of the lower boundary.

Standard: AD&D2, D&D4, Mekton II/Z, BESM2.

BESM3 may be a good representation of the upper boundary.


Rules Heavy

These games may or may not have a universal mechanic, but they often have multiple subsystems which don't use this standard.  There are often rules for minutiae which doesn't come up often in game, and standard game activities are detailed to the possible point of overkill.  There are often lots of little exceptions and special rules conditions littered about the rules.  Characters regularly take multiple pieces of paper.  These characters usually take about an hour to create.  Explaining the game often takes about an hour for a newbie.  Learning to GM the rules effectively often takes weeks of study.  The books are often heavily laden with hard rules and frequent charts.  Multiple volumes of core rules are very common.

A Palladium System organized and written by a person who actually knew how to write might be a good example of the lower boundary of Rules Heavy.

Standard: AD&D1e, D&D3e, Hero System, MERP.

So, rules half assed or rules incomplete equals rules lite?  I disagree, of course.  My personal outlook tends towards looking at the actual number of data manipulations, methods, and individual processes involved in using the game.

It wouldn't be fair to include long arguments about how things "really work in the real world" though that's the biggest downside I see to incomplete systems.

Its something so highly subjective.  To me, rules "light" is Over the Edge or Amber or Everway. D&D is rules-medium in most cases.  But other people's choices will vary wildly.

RPGPundit

Going on games I have played, where I would place them on how we found them in play.

Light:
Fighting Fantasy, Mongoose Lone Wolf (not D20), D6 (Star Wars), v6 (Stomic Highway), Castle Frankenstein
Medium:
World of Darkness*, Roll and Keep (7th Sea), Savage Worlds, WFRP (real), PDQ# (Swashbucklers of the 7 skies), OD&D, Rolemaster, Doctor Who (Cubical 1), Fading Suns*,
Heavy:
Cyberpunk, Ars Magicka, d20*, Deadlands, D&D (4th), WFRP (ffg), Prime Directive*,

*are games with a wide variance based upon specific ruleset, GM, group, whatever.

Obviously, these are wide bands, but i think the most telling characteristics are how many times the rules have the be explained to the players per session, how many times the rules need to be read per session and how much GM prep is expected.

Quote from: Rincewind1;527877For me, the key elements to distinguish between a rules - lite vs rules heavy system are:

1) How long will it take for me to create an NPC from scratch?
2) How often do I need to reference from handbook during game?
3) Amount of very situation - specific rules that I'd need to memorise.

I think that this is a good metric, especially when you tie-in familiarity with the system at hand.