I don't see how other games are relevant as they aren't claiming to be part of the "D&D tradition."
Some are. For instance, 3E claims to be part of the D&D tradition, though over time, as I learn more about and think more about in comparison to 1st ed AD&D and other classic versions of D&D, I find it to be a greater and greater departure from the core of those games.
I didn't mention OSR games, but obviously they claim to be part of the "D&D tradition".
And then there are OGL/SRD games, of which I mentioned one - Trailblazer - which obviously claims to be part of the D&D tradition, in much the same way as PF does.
A game like Rolemaster is also within the D&D tradition, thought it's a different (and perhaps now largely extinct) branch of the tradition - it has classes (like D&D) and a spell system based heavily on the D&D one, and is intended to appeal mostly to people who enjoy the basic fantasy tropes and outlook of D&D but want something different from (taking the RM perspective, the phrase would be "sophisticated than") D&D's mechanics (eg robust skill system, less strict class definitions, more nuanced and gritty combat - ie much of the stuff that Monte Cook brought to 3E).
In light of 3E it's easy to look back at a percentile system like RM and see it as obviously not D&D, but when RM was written (early 80s) D&D wasn't a d20 system. Thief skills used percentages, clerical turning used a d20 in AD&D but 2d6 in B/X, and Moldvay's examples of improvisation involved assigning percentage chances - [MENTION=6680772]Iosue[/MENTION] will be able to correct me if I'm wrong, but I think the idea of a stat test rolled on a d20 was introduced in the Expert rules rather than Basic.
And in view of ICE's TSR-style demise in the late 90s, and its current existence which is really at best a lingering on, it's easy to dismiss RM altogether - but in the late 80s ICE was the a big RPG company (on the back of its Middle Earth licence), with full-page ads on the cover or splash page of nearly every Dragon magazine (more info
here).
Then there are systems which mechanically depart from D&D but set out to capture (and perhaps improve on) what was, for the designer, a key part of the D&D experience. Burning Wheel, for instance, references AD&D 2nd ed in its designer influences, and also references 4e in a more recent volume. And the designer (Luke Crane) is quite overt in explaining what features of D&D his sorcery system and Faith system are intended to emulate.
TL;DR - there are lots of games that have, in the present or the past, presented themselves as "alternative visions" of D&D. They haven't all created edition wars of the sort you're talking about, though.
D&D before 4E had a long, 34-year tradition, which many viewed it as breaking from.
I don't find the language of "breaking from tradition" very helpful, though. It is very normative, but on no very clear foundation.
For instance, 3E changed the rule that hit dice and CON bonus stopped at name level. It changed the rule that a wizard can't use a sword (s/he can, just with a -4 (?) to hit). Conversely, 4e harks back to Gygax's essays on the metaphysics and game-mechanics of hit points and saving throws.
All revisions to D&D involve
changes. But classifying them into ones that
break with tradition and ones that don't is fraught. Frankly, it strikes me as ex post projection onto the past.
Imagine if, instead of dropping 3.5 for 4E in 2008, they had instead come out with a separate line called D&D Empowered, or something like that, which was basically 4E.
It probably would have fizzled - at least, that's my guess. 4e was promoted as a core system, with all the market support that brings with it (organised play, DDI, etc).
Then they gradually taper 3.5 off for another couple years until them come out with the new edition, which resembles something akin to what 5E is, in 2011 or 2012. I'm not saying this is what I think they should have done, nor what I wish they would have done, just that it is an interesting thought experiment.
I can only assume that tapering 3.5 off was not feasible for them, because if it was they would have done it. It's not as if they weren't configured to produce 3.5 material!
And we did get something akin to 5e in 2011, namely, Essentials! The degree of kinship is of course a matter of contention - Essentials as a design somewhat falls between two stools, and it suffers further from non-design issues to do with how the content was put together and marketed. (About 3 books worth spread over 5 volumes.)
Everything about 5e's design suggests to me that WotC took seriously what it learned from its market reserach. And I agree with [MENTION=22779]Hussar[/MENTION] that they used the playtest very effectively to shape and manage, as well as respond to, consumer demands.