I’m in the group that looked at the poll and couldn’t answer, because it is so squarely in the middle. Now, if there were a free pizza impelling an answer from me, I’d say “heavy”, but I’d probably wince.
I’ve got a pretty broad knowledge of role-playing games (not as much as some of you, but more than most gamers) going back to late 80s. (That’s context for my observations, not a claim to authority.) From *my* perspective light or heavy games are something I can clearly place in that category. If I can’t easily place it one way or the other, it’s moderate/medium. (I think the same way about D&D alignment, or at least the L/N/C axis.)
GURPS, HERO, or the occasional behemoth of a rules set that makes your head hurt and yours eyes water trying to use—those are heavy. Pathfinder is probably on the lighter side of heavy too. (I know someone is going to say it is way heavier than GURPS, and they’re probably right, but it’s been a while.)
Most games that are clearly in my definition of light aren’t all that popular. Off the top of my head, I’d place Marvel Heroic Roleplaying in that category, about 75% of the way to medium. There are a slew of really light games out there that very few people know about. I’m sure I’m not the only one who has created ones you can write on one page or less. However, I think most of those should be given less weight than the proliferation would indicate. Why? Because how often do they actually get used regularly by any significant number of people? If they aren’t satisfying enough to be regularly played ( rather than simply used as concept proofs and design exercises), then I’m not going to average them up and account for them in some sort of mean average heaviness result.
However, I don’t think a pure median average works either. If there is one game that is an order of magnitude heavier than everything else, it shouldn’t skew of the overall scale, just like “Here’s the rules: everyone says what happens in the story from the perspective of their character. We’ll call it Game”, shouldn’t set a low-end standard for lightness.
So what all that analysis is telling me, is that there is an intuitive feel that helps me sort through the thoughts in my head when I’m determine how heavy a game is. But what I think the feel is based on is how complicated it feels to actually play the game, combined with effective learning curve. Number of product pages is irrelevant to that, but number of distinct subsystems is huge. (That’s why I don’t count older edition of D&D as light, because subsystems for things like bending bars and lifting gates is a mess of complexity.)
I will say I probably count D&D as a little lighter than it should be due to familiarity. I can look at 5e and see how it is lighter than other editions, but someone who has never played D&D but has lots of experience with GURPS might find 5e D&D a heavier game. (I might even agree if it hadn’t been so long since I’ve looked GURPS.)