Genre emulation can go a lot of different ways, depending on your source material. The whole "Appendix N" fetish, silly as it can get, sheds a lot of light on OD&D/1E design decisions: though DCC RPG is the best I've seen at genre emulation.
The three Appendix N authors whose works I know well enough to comment are JRRT, REH and HPL. And for what it's worth, I don't think classi D&D (original, Moldvay Basic, Gygax's AD&D) does a particularly good job of emulating them.
I think the non-emulation of JRRT - in terms of magic, motivation, etc - is sufficiently evident that I'll not elaborate. The non-emuation of HPL is also pretty commonly remarked upon (eg "magic"-use doesn't drive you mad; eldrithc horrors are often rather easily defeated, and often are not a source of terror; etc).
But I also think the system doesn't do very well at emulating REH. One reason is that powerful fighters aren't powerful enough relative to powerful wizards, who carry over too much of their Chainmail artillery-substitute baggage, rather than the sort of "alchemy and rituals" stuff that is seen in REH's wizards.
But a second, and more serious, is that the REH Conan stories are all about a protagnist who acts spontaneously, takes risks, and is largely indifferent to whether or not those risks pay off (eg in The Tower of the Elephant, or The Jewels of Gwahlur, the treasure is lost but Conan is satisfied that he has done the right thing). Whereas classic D&D play - the underpinnings of which are set out clearly by Gygax in the closing pages (prior to the Appendices) of his PHB - is all about cautious preparation, minimising risks, and ensuring that the treasure is collected and carted out down to the last copper piece.
If I wanted AD&D to emulate REH's Conan at a minimum I would need to radically change the XP/advancement rules, and give the players some sort of "fate point" or similar mechanic that they can use to trigger an advantageous chance encounter (such as happens with the dungeon guard and then Pelias in The Scarlet Citadel, with the hillfolk in People of the Black Circle, with the witch in Hour of the Dragon, with Epemitreus in The Phoneix on the Sword, etc).
Balance in terms of contributing is also on the DM; reliance on a good DM is, for me, the core strength and heart of TTRPGing
I don't think anyone seriouisly disputes the importance of the GM to RPGing.
But that doesn't settle the question of what the GM's function is.
Consider the examples I gave from Conan - of course, the GM could just throw in a chance encounter with a Witch, or a dungeon guard who wants to slay Conan out of revenge and therefore (inadvertantly) provides him with the means of escape. But for some RPGers - including me - that is not all that satisfying: first the GM sets up an encounter in which the consequence is that the PC loses (eg ending up in prison), and then the GM hands the player the means of undoing that adverse consequence. This makes the player seem essentially like s/he is just along for the (GM's) ride.
Whereas if the
player has the mechanical werewithal to trigger the encounter (by using some player-side resource or capability, like a BW Circles check), then it is the player's choices (both in build and in play) that drive things. And the GM is just as apt to be surprised by the upshot as the players are.
Of any edition of D&D, 4e does the best job of facilitating that particular sort of play dynamic, as it has the most robust tools for allowing the GM to frame challenges which s//he knows the players have the resources and capability to meaningfully engage, and for allowing the players to engage those challenges in a way where it is their choices (both fiction-oriented and mechaincs-oriented choices) that will determine the shape and content of the resulting ingame events.
Which then takes me to . . .
"Balance" and "reliability" are fairly vague in this context: results on any edition can be charted for probability, so they are "reliable" in that sense
The results of an action declaration "I sprint as hard as I can to head off the goblins" can't be charted for reliability in AD&D, because there is no mechanical system to resolve it.
For the player of the fighter in my 4e game, on the other hand, it's reliability is very knowable - if he has Might Sprint unused, and uses it, then he'll make it; othewise probably not.
Even within the context of improv mechanics, 4e is also more reliable because of its DC-by-level and Damage-by-level charts. It's easy to call for a Medium Athletics check, for instance, to move an extra square, and to tax the character a level-appropriate amount of damage if the check doesn't hit the Hard DC threshold.
This player-side reliability; and GM-side ease of framing situations that engage the players both thematicallly and mechanically but leave the actual outcome as a result of player choice plus dice rolls; is what enables the sort of non-GM-driven play that I described above.
When you say "4e does the best job in DnD history of modeling such characters in a mechanically satisfying way" rather than "relying on player imagination to model the thematics" I feel I see the difference in our play styles and experiences, because the latter is how I prefer the game to play out, and when I was saying "tactical" perhaps "mechanically modeled in detail" is a more accurate way to describe it
I don't see 4E as having been "better" or "worse" in some sort of "objective" way at helping people pretend to be elves with friends, because you don't need "rules" for that, even.
if the mechanical fiddly bits helped y'all get into the RP aspect, awesome. But I can RP while playing Monopoly or Chess, it's a human attitude not a mechanical effect.
While playing Monopoly or chess you can say stuff, and you can project imaginative events onto the ingame situation. Monopoly lends itself better to this than chess, I think; and a CCG like M:tG, or the LotR ones (I know of the Decipher and the earlier ICE ones) even moreso.
But in none of these games does that "roleplaying" have any effect at all on resolution. It is simply colour. Change it, and the game plays the same. Don't do it, and the game plays the same.
What is distinctive about RPGing, as invented by Arneson, Gygax, and co is that - like some (but not all) wargames, the fiction
actually matters to resolution; and - unlike a traditional wargame - the players engage the game through the persona of a single distinct individual.
In 4e, these two elements are very tightly integrated, because the resolution mechanics express, and establish, in an iterative fashion, the persona of the individual character. To borrow from [MENTION=6696971]Manbearcat[/MENTION]'s example above, we know that the character has a depth of grit and willpower that will come to the surface when the chips are down, because
when the chips really are down, the player uses Strong Focus to (try and) save the day.
D&D has always had some PCs - namely, casters - who can choose abilities that express their personality (contrast the cleric who memorises Raise Dead with the one who memorises Slay Living). The game has never just had a generic "Cast spell" ability which relies upon the player to overlay some colour in order to establish what is going on in the fiction (ie its spellcasting system has never resembled its traditional combat system; contrast, say, HeroQuest revised in this resepct).
But 4e develops this system in two ways. First, it extends it to non-caster characters; so their players, too, can build up combinations of elements that help tell the story of the character. Second, by emphasising "encounter" powers, and correspondingly reducing the importance both of at-will abilities and nova-ed daily abilities, it gives much more weight to a feeling of "trying", or heroic effort, on the part of the PCs. And by increasing this sense that individual choices that are made in the course of play are also expressions of the personality of the character under pressure, I think it tightens that connection and feedback between mechanical resolution and PC persona.
Which also relates to [MENTION=82106]AbdulAlhazred[/MENTION]'s post upthread about 4e tending not to "stall", or have moments where no one is quite sure what the next move is. It produces a very different experience from a sense that everyone is just sitting around shooting the breeze and making some stuff up, and the game itself is not doing much more to underpin or direct that than would a game of chess or Monopoly.