Tabletop games in general tend to suffer from this over time, partly because of a very simple dynamic. If a game gets some success, fans tend to like its traits. The designers may not: they probably had numerous kludgy hacks and flaws that irritate. Regardless, a 2nd edition usually expands and smooths over the game. Designers will then become somewhat less tolerant of the things they couldn't get rid of previously. A 3rd edition will become somewhat more complicated in ways which often mystify players but also overly-simplify many of the more fun aspects of the game (frequent and often over-used nerfing tends to occur). A 4th edition often sees the designers (possibly an entirely new crew) rip out the entire game and rebuild it. This can utterly change the game, and the dynamic is not always improved by the fact that the later designers often started as fans of the game. Major examples include Dungeons & Dragons, Shadowrun, and The World of Darkness.
This also happens to video games: Civilization slowly got more complex, with more techs, until the fourth game reduced the number of techs by redoing everything.
Every time Dungeons & Dragons changes editions, a large amount of the fanbase decides to rise up and complain about how everything has been ruined. This is more true for the changes from 2nd Edition on up, but people complained about the switch between the first and second editions as well. 4th Edition has prompted more shrieks of "D&D IS DEAD" than ever before due to an extreme case of They Changed It, Now It Sucks fueled by pure Internet Backdraft. All that said, this isn't the place to discuss whether it has in fact been ruined, or not. Please Take It to the Forums.
Gamers don't even need to wait for edition changes anymore. Wizards of the Coast, the company that currently owns D&D, publishes "rules updates" every few months, which include genuine errata (i.e., corrections to mistakes that have been noticed since the last update, changes made in the last update, or books published since the last update), as well as changes to things the game designers have noticed that players have been taking advantage of, changes to whatever the online fanbase has been complaining the most about recently, and - most controversially - changes to things the game designers have just kind of decided they'd like to work differently. Those last three elements often involve completely revamping popular character options and frequently invalidate popular character builds, making Dungeons & Dragons 4eRuined Forever every few months. Now the Essentials release has fans up in arms all over again.
5th Edition has been announced, with most being hopeful it will be more like 3.5 (with better balance and some rules reworked), though fans of 4e are in arms about how they'll have to buy all new books and no one will want the old ones - much like older fans had done previously. Unfortunately, in its current playtest form, the balance is worse than 3.5. Also the fact that the old trap of Linear Warriors, Quadratic Wizards had been successfully escaped in 4e (more or less, for better or worse) by giving non-magic classes diverse utility skills and combat abilities. "D&D Next" has them with mechanics to swing their preferred weapons and everything else basically up to DM discretion, meaning the LWQW trope could still be averted or played disastrously straight, depending on how flexible the DM is.
BattleTech has had many of these. Depending on the specific fan, these include (working roughly backwards):
The Jihad (oddly, the same folks who previously decried the unrealistically small armies in the universe screamed the loudest when one Genre Savvy faction went ahead and built a large force)
The Fed Com Civil War (specifically, its end, with both nations remaining separate)
The Twilight of the Clans and the destruction of Clan Smoke Jaguar (at least for the Smoke Jaguar fans, even though the Clan had been set up as clear bad guys)
The breakup of the Federated Commonwealth (some folks just wanted a winner, even though it'd mean that the storyline would've effectively ended)
The loss of the rights to the "Unseen" images (despite a major legal battle that established several precedents in copyright law. Also, this complaint has effectively disappeared — one hopes — now that the Unseens have been licensed again and are available for use in Battletech artwork.)
The Clan Invasion (despite it being planned by the original authors from the very beginning, and very clearly foreshadowed)
The "timejump" of the Twenty-Year Update (mostly in retrospect, and despite new material being produced for that time period)
The Fourth Succession War (though it was the lead-off storyline)
The rebranding of the game from "Battledroids" to "BattleTech" (despite that it only existed as the former for about six months, and the threat of legal action from George Lucas)
Most perplexing, some fans decry events that only occurred in the off-screen backstory, such as the destruction of Clan Mongoose or even the Amaris Civil War, even though the latter is the entire foundation of the universe.
The fall of the HPG network, and everyone attacking their closest targets has some fans cheering for their fav side winning, and others who want their side to get the upper hand.
Every time a new army is released in Warhammer or Warhammer 40,000, cue cries about how said armies rules are ridiculously unbalanced, how every other army is now worthless, how their upgrades are so incredibly unfair and, yes, how Everything Is Ruined Forever. Because gods forbid you might actually have to rethink your strategy for once.
Or there's the second time they changed the rules of 40K. The first time, WH 40K was a niche title with a rulebook named Rogue Trader. The second time, 40K was a TV-advertised product which therefore had a sizable fanbase. The ensuing drama has probably caused a dimensional rift somewhere.
The Tau empire doesn't shoot everything they see? AND they're reasonably diplomatic?! 40K IS RUINED FOREVER.
This was later retconned to something more appropriate.
They changed the Tau? More like they RUINED the Tau (forever)!
The biggest example of this in Fantasy was when 7th Edition Daemons were released. The entire fanbase cried RUINED FOREVER! Daemon players because they completely revamped the fluff, the playstyle, the models and removed the 'One God' requirement. The rest of the players cried RUINED FOREVER because Daemons were the single most broken army in the game. The result was they kept ramping up EVERY army they updated to try and compete with Daemons, but nothing could stop them. They finally revamped the entire rules system to try and fix it and things got more balanced...a little.
Even before nWoD, this was happening - notably with the revised edition of Mage and Kindred of the East.
However it seems like there's some agreement that Changeling and Wraith/Geist completely invert this trope, as they are often seen as better... though the older games still have their RUINED FOREVER people.
Exalted - especially with Dreams of the First Age's Solar Charms (universal) and with about half the Ink Monkey articles (opinions widely differ).