Back in the very early days, before I had seem much besides D&D and maybe a little bit of Champions and Traveller, one of the things that widened my eyes to the broader hobby was a copy of Ian Livingstone's Dicing With Dragons, which was an interesting book in a lot of ways.
RuneQuest 3 rubbed a lot of existing RQ fans the wrong way and bashing it in favor of RQ2 was the hip thing to do for many years. It added a few new rules that some felt cluttered up the system, but more importantly it distanced the rules from Glorantha — one of the finest settings in the history of RPGs — as the default setting. I was unaware of any such drama at the time, of course, having never seen a live RQ2 book in the wild and therefore having no appreciation, except by vague hearsay, of how good some of that early Glorantha-based RQ stuff had been.
Time and a collecting budget gives one new perspective. But to this day I still feel that RQ3 was a better implementation than RQ2. The rules changes were almost all minor, and the big one, Sorcery, was a significant and welcome addition. The separation of RuneQuest from Glorantha, though, was very important and, I would argue, a good move for the game.
I think it can now be seen much more clearly that even in the early days there was a tonal disconnect between historically-colored, gritty RuneQuest and dreamy, mythic Glorantha. RuneQuest just wasn't an ideal match for the kind of game that Glorantha was increasingly being designed for. That had to have been a factor when the time came to design a new game system for Glorantha, when it appeared that RuneQuest was lost forever in the mire of Hasbro's buyout of Avalon Hill. The resulting game, HeroWars, which developed into something pretty terrific in its own right in time, was nothing at all like RuneQuest.
The second reason is why I personally prefer 3rd edition over 2nd; RQ is a marvellous and very powerful engine for simulating a wide variety of fantastic and historical settings. I think tying it to a single milieu obscures that. It's one of the only games to treat magic in the same way as it's handled in, say, the Icelandic sagas; not as some arcane art practised by some dusty wizard shuttered up in a tower, but as one of the facts of everyday life in a world seen as mythic by its inhabitants. Anyone might throw a hex or cant his blade to sharpness, or invoke the blessings of a harvest goddess. All while not neglecting the power and subtlety of the dedicated practitioner.
Just when it seemed that RuneQuest might be dead forever, it came back in the guise of a new edition from Mongoose. This was, I would argue, a misfire in some respects, because the Mongoose edition of the rules took a good part of their core flexibility away and shunted it into supplement bloat. The core book felt like crippleware. Although everything that was lost eventually came back, I didn't feel Mongoose did right by RuneQuest until their second edition, now called MRQ2. But it resurrected RuneQuest as a viable brand after years in limbo. And very interestingly Mongoose opened up RuneQuest via the OGL, allowing them to continue publishing the MRQ2 rules as Legend after they lost the rights to call it RuneQuest... and allowing me to pilfer from it for An Age Undreamed Of.
After Mongoose the game went to Design Mechanism, which put together a 6th edition that is absolutely terrific, playing to all of the strengths of every edition of the game. It is a weightier system than RQ2, for certain, but it also does a lot to model almost any setting inspired by history and roughly realistic in tone. More importantly, it places characters firmly in the context of their societies within those settings, one of the game's traditional virtues.
Its five magic systems add a ton of flexibility, lacking only something more strictly along the lines of Stormbringer-style summoning... but you can import stuff from other BRP iterations easily enough, or build it from the tools already in RQ6. For clarity the book is second to none. I find myself in desperate need of this volume in hardcopy.