It's amazing how often I hear roleplayers say something like "We had a great game of D&D last week, we went the whole session and never used the rules once!" This kind of statement puzzles me. How, if you're not using the rules, could it possibly be considered a game of D&D? Sure the trapping are there, the setting, the rulebooks, the character sheets, the dice, and so on. But if they weren't used, then the actual game certainly wasn't D&D, it was something else entirely.
What they were actually playing, to my mind at least, was their groups social agreement. That often unspoken part of the game, where players agree where the limits are, who can contribute when, and what the limits of the setting and story are.
Now at this point you may be saying, "but we always go by the rules!" And if so, then good for you, that probably means your group's social agreement fits quite nicely with the rules you are using. But think back, when was the last time your GM fudged a dice roll instead of killing a character? Did you let it slide, accepting that this is how things are done, or complain that he cheated? This is a prime example of the social agreement that players should be heroic characters who don't die arbitrarily, overruling the system's rules of character death.
Does your GM allow other players to interject with cool story ideas? I do, it's not part of the rules, but it's an accepted part of the games I play in. If I did it in some peoples groups they'd probably look at me funny, why is he suggesting how his Call of Cthulhu character dies?
Many roleplayers seem to ignore the fact that large amounts of the game rules are un-spoken. That the rules are built into the social dynamic of the group, rather than the rulebook of game they are playing. Long term gaming groups tend to adopt a style that they are happy with, and stick to it. It doesn't matter if they're using Fudge, D&D, Vampire, or GURPS, because they have this unspoken agreement on how they play. In fact it really doesn't matter which game they are using.
For a long time this led me to believe that any new RPG was only useful for acquiring new setting ideas, since most groups would just ignore the system and only play the bits that they liked (i.e. the bits that worked best with their social agreement).
Then I had an idea. What are rules if not a social agreement on who gets to say what happens and when?
So perhaps all those games with rules you don't like, or can't find the sense in, are just the game designer trying to give you their model of the social agreement to play with. To try differing levels of control among players and GM, to try games that focus more on the game, or more in the story than you normally would. As long as the players agree that they want to accept the system's priorities, they can try out a new approach. Of course what normally happens is that players take one look at a system, decide before playing it that they don't like it, and ignore it, returning to their default social agreement.
So what is my conclusion here? Not a great deal other than this: Play a game as written before you fudge or tweak anything. Just because it doesn't seem to work on paper, doesn't mean it's a bad idea, just that it's trying to encourage a style of play that is different from your current prefered style. Try it, who knows, you might be pleasantly surprised.