While I haven't taken part in any edition wars, I have noticed some things that I think have contributed to negative sentiments some players have regarding various editions of the game. For example, I believe that one of the main factors contributing to criticism of 4th edition D&D is quite simply the graphic design choices and "fluff" choices that the game designers made in the construction of that rules set. I believe that Robert Schwalb's observation are essentially correct . You can see an example of how Robert would have reformatted some of the information here. It's a little rough around the edges, but you can quickly see how 4th edition could have been formatted to look more like previous editions.
No where is this more evident than in the presentation of monsters. For over 30 years the Dungeons & Dragons game had been increasing the amount of "fluff" in its monster entries. Early editions of the game had minimal information scattered over many pages - or even a couple of booklets. By 3rd edition there was a combination of beautiful and useful statistic blocks combined with ample ecological and sociological data about the monster that was being presented. 4th edition - prior to the publication of the excellent Essentials Monster Vault: Threats to the Nentir Vale - completely reversed this trend. It returned to the earliest days of presenting monsters as little more than a set of numbers. I believe that this was one of the primary reasons players thought that 4th edition was less able to facilitate "role play" instead of "roll play" than earlier editions. I have often argued the opposite as page 42 of the DMG and the Monster Manual on a business card are almost everything a DM needs to run 4th edition. The DM can wing the rest and up the role play all day. I have argued that many times, and believe it to be true, but I cannot argue that the presentation of the monsters as mere lines of numbers doesn't convey the sense that "role play" was far less important in the minds of the designers than "roll play."
I think the best way to demonstrate the history of monster presentations in D&D is not a discussion, but a demonstration. The following are stat blocks from the various editions of D&D selected to highlight how each edition added depth of presentation to the monsters...until 4th edition...and how 5th edition has restarted the tradition of more detailed entries with greater verisimilitude. One caveat. The entry for OD&D was pieced together by me from information contained on multiple pages in two booklets. Those booklets are Book II: Monsters and Treasure from the OD&D box set and the Greyhawk Supplement. I own physical copies of all the books featured in this article.
The OD&D Gnoll features very little information about Gnoll's as a creature and the illustration makes it difficult to visualize what kind of creature this actually is. The reference to "Lord Sunsany" (Dunsany?) not making clear what Gnolls are like only ads confusion to the reader. There is room for the Dungeon master to expand on the information, but there is no context for the creature and it is primarily being presented as a set of numbers that players can fight. The "number of attacks" and "points of damage" information come from the Greyhawk supplement as all attacks did 1-6 in the primary OD&D rulebooks.
Advanced D&D Monster Manual
You can clearly see a radical shift in emphasis between OD&D and the Monster Manual. Gygax not only describes what the Gnoll looks like, but provides sociological and ecological information. We know where Gnolls live. We know a little bit about their social structure. We also have a better illustration of the creature.
The Moldvay Basic Gnoll is very similar to the one presented in the OD&D boxed set. This is likely due to the introductory nature of the rule book. It should be noted here though that the presentation here is cleaner than in OD&D and that there is some description of appearance and mannerism. It isn't as complete as the Monster Manual, but it is still a step up from OD&D.
Second Edition Monstrous Compendium
By Advanced Dungeons and Dragons 2nd Edition, TSR was providing a great deal of information about their monsters. This Gnoll entry takes information from the earlier MM and organizes it into a more cohesive order and provides some roleplaying information about Gnoll behavior. This is a very useful stat block.
Third Edition Monster Manual
The 3rd edition Gnoll has excellent art, but after the 2nd edition Monstrous Compendium's single page per monster layout the need to flip between two pages to get the information is less than ideal. The description provides a number of interesting bit about society and appearance. There is also a good section on how to use the monster in combat. Notice here the inclusion of factors like "reach" which comes into play for the attacks of opportunity. This has the best art so far. The 3.5 rulebook is similar with added information regarding level adjustments and Gnolls as characters. The stat block section is considerably larger in 3.5 due to the inclusion of information regarding "touch" and "flat footed" armor classes. All of which is done to speed up play in a tactical game by removing from the DM the need to do math on the fly.
4th Edition Monster Manual
First, let me say that there is some cool stuff in here. There are multiple types of Gnoll, each with distinct attack types. The art is more cartoony than 3rd, but I really like it. If you want to run combat, there is good advice. If you read the "Gnoll Lore" section, there are some interesting tidbits. BUT...everything is presented related to some mechanic. The Gnoll Lore is given in increments based on skill checks. It isn't narrative fluff, it's "stuff you roll for." Encounters are set up including terms like "level 8 brute" which means almost nothing to the new gamer and makes it seem like you are putting together a Warhammer Fantasy Battle or Warmachine group. And that's the crux of the ire right there. The entry focuses on the mechanical and miniature wargame elements of D&D. Is there stuff that makes for good role play here? Sure. Take this quote, "slaves who show strength and savagery might be indoctrinated into the gnoll vanguard." That's pretty cool, but it requires a DC 25 to know. Huh? The DC to know set up was something that I largely ignored in 4th edition, just like I ignored "segments" and "weapon vs. armor type" in AD&D (though a recent issue of Gygax Magazine demonstrated that at least Lenard Lakofka uses them in his games).
What About 5th Edition?
It looks like they've returned to - and taken a step further - the presentation style they used in 3rd edition and merging it with the ease of use of the 2nd edition presentation. This post at Critical Hits shows the Bullette and this one from Dread Gazebo shows the Umber Hulk. Wizards of the Coast has been kind enough to provide us with the Sphinx.
If you want to know why I'm so excited about 5th edition. This is why. There is a full page of narrative description of sphinxes that also includes an inset of the riddle from a classic AD&D module. The art is very good and the layout is wonderful. The stat block tells you a lot about the new D&D edition. Check out that Armor Class. It's only 17 for a Challenge 17 monster. For a 4e player, who is used to AC increasing by one per level or for a 3rd edition player who is used to Fighters adding +1 to hit every level, this must seem quite low. In fact, it isn't for 5e. Yes, the monster is likely to be hit fairly frequently by appropriate level opponents - but the 199 hit points will help it stick around. Also examine that section on Legendary Actions. This is a modification of one of my favorite developments in later expansions for 4e, monsters taking actions during an opponent's turn. In this case at the end of an opponent's turn. The stat block also isn't as reliant on miniatures based mechanics as the 4e block. I've written a couple of posts on "Zones of Control" for this blog that demonstrate that D&D has always been a miniatures war game, but it has typically been one where one can ignore that element and move on with game play. 3.x and 4e made that more difficult than earlier editions, but we seem to be moving back toward a nice balance.