Well not 'ruined' necessarily, but games that are so good that other similar games don't seem as awesome anymore.

Personally I can think of 3 examples:

WoW ruined Everquest 2 for me
EQ2 always seemed like the better mmo on a technical level, but the world of vanilla wow just had an incomparably cooler vibe for a warcraft junkie like me. There wasn't anything in EQ2 that could compare to just taking a leisurely stroll through Elwynn forest with its amazing background music.

Cataclysm:DDA ruined Project Zombie for me [edit: sheesh, I meant Project Zomboid]
PZ is an awesome game, but after checking out C:DDA I don't think I'll ever be able to go back. Not only does it have NPCs and vehicles (both of which are in high demand on the PZ forums), but it also has : rampaging moose and wolves, mutant death frogs, giant snakes, many different kinds of zombies, killer robots, mininukes, cyborg implants, secret military/scientific installations, and the list goes on and on. Come to think of it, it's pretty much an ascii version of PZ set in a Fallout type universe. Oh yes, and you can build your very own Mad max type death vehicle to store your stuff and run over zombies, or other npcs, or squirrels...

Oblivion ruined Morrowind for me
I've tried returning to Morrowind several times, but it just bothers me too much that several(most?) npcs are frozen in place compared to each npc having a life of some sort in Oblivion: They get up, pursue some sort of activity that may differ from day to day, and then go to bed at night. It does wonders for immersion.

Cultures 2 ruined the classic Settlers games (up to 4) for me, because for me it was the same game with a twist of life management and RPG.

Might and Magic VI did that for me, especially in regards to I-V that came with it in the 6-pack limited edition. I played 6 first because that's what had been installed and was being played by my roommates. Interestingly, I also couldn't really get into the later versions, 7-9, (or however many there were after 6) and never played them.

I've pegged that to the portraits in M&M6 used for the party members, and for the avatars for NPCs in the houses and castles. Portraits of real people (with zits!), though a lot seemed like portraits from renaissance fairs and such. The party member portraits were obviously photographed for the game itself, likely with stage make-up for when they were to appear as diseased, poisoned, or beaten into unconsciousness. It took me a while to realize, but I do believe it's that aspect of real people, even if only photographs, that has gotten me attached or nostalgic more so. Perhaps because I could care about them more than a cartoon? They look like they were getting hurt because they were actual people. And cartoon characters never really get hurt, do they? Or at least that's what I've come to believe, but that might have been some misinformation I'd gotten long before.

In later versions there were computer animated portraits instead for the party members and NPCs. Perhaps too symmetrical? Or no zits or pimples? I mean, how hard would it have been to get some Spock ears and make a real person look like an elf? But no, they didn't bother. As such, I guess any other computer or console game since 1999 feels lackluster with their digital creations instead of real people. And it's not like M&M6 had fantastic graphics for the characters walking about, it's instead the avatars that showed the intended representation that helped my imagination bridge the gap from cartoon or computer graphic to an emotional reality. Well, at least that's what I'm figuring lately and why even the latest games (even videos of "virtual reality" games) feel like they're...too unreal? Perhaps because they rely upon drawings instead of photographs, even if they are computer drawn drawings?

I only played the first Cultures, and though I like the life management, it weirds me out a bit how you can go through several generations of vikings without the first generation aging/dying.

I'm more at the opposite end of that: if I find something awesome I immediately start looking for games that are similar, because I rarely want to play the same game many times over, especially in one stretch. I mean, playing through Master of Orion twice is fun, but after that I'd switch to something like Star Ruler or Galactic Civilizations. In my mind I tend to single-out what makes each game unique.

I know a large number of gamers experience what you describe though, they find something that is perfect for them and hence loose interest in "contenders". I've rarely experienced that for myself though.

Edit: the best case I can come up with is Mass Effect 1, which was more or less a perfect game for me, the other Mass Effect games just didn't hold up against this.

I have to agree with this. I have been playing Morrowind recently, I have been having fun but there is very little immersion there to be had. Every character has a stick up their ass and don't move. How dull.

Oblivion improved upon considerably it seems. Fun games never the less.

Fallout 4 spoiled New Vegas for me. After getting fed up, I went back to FO4 just to see if I was missing something and played the shit out of it. It made me realised what a boring buggy sack of shite New Vegas is. Very little character, very few interesting environments, so many invisible walls and so little to do.

Down rated in 3... 2... TRIGGERED!!! I Also agree with Mass Effect. The sequels were such let downs that I couldn't hack any more of them.

You mean like "Das Boot" murdered all the previous (and future) ww2 submarine movies ?

It didn't happen much to me, because my love for old flawed gameplays and interface is a bit abnormally solid. I would say that "Swat 4" and its fast context-sensitive orders systems made me forget why I enjoyed "Swat 3" so much. But I still intend to rediscover this.

More generally, I was about to say that the advent of open area FPSes ("Outlaws" and then "Far Cry") killed corridor shooters for me. It's mostly true. They made it hard to enjoy "Doom 3", "Half-Life", etc. I now need the swashbuckling feel of sneaking around the baddies and find an unexpected angle of attack instead of charging their ranks headfront. But still, the likes of "Fear" and "System Shock 2" are corridor shooters, and they survived pretty well.

And sometimes I feel like some absolute games such as the "Total War" or "Men in War" series render whole genres obsoletes. I could so easily claim so. Who needs RTSes when you have these ? Well, I still suprise myself enjoying a basic RTS sometimes. But "Dune 2" is dead though. Murdered by the first RTS with mouse-drag multiple unit selections. I have no memory of which game first introduced me to that system, though.

You remind me of how awesome the real life council from civilization 2 is : https://www.youtube.com/watch?v=XqPC08cPGJw

I totally get what you said about it helping your imagination to bridge the gap between the computer graphics and reality. But from what I've seen growing up it can work just as well with more detailed computer graphics instead of real life videos/photos. Dune 2 is my favorite example. For instance, the house of ix is a tech building in Dune 2. In the screenshot from the base it's the little blue building at the bottom center, and the other screenshot shows what it looks like in the construction menu which is meant to show what it looks like in 'reality'. In the latter you can get a genuine sense of scale of the building and that, together with the animated images of each of the other buildings and units completely transformed the vision I had for my base. Unfortunately it didn't catch on in the rts genre and the construction menu with the artwork for each building and unit died, as far as I know, with Dune 2.

I'll have to try this, I'm always looking for decent roguelikes :)

On topic... I don't know really, I can't think of too many games where I've thought "This is so good I'm never playing game X again"

I suppose the closest thing is RTS games, I find it really difficult to go back and play older ones because the genre has come on so much and older games that lack the convenience features of modern games seems so clunky now.

I could say that Final Fantasy 5 ruined FF6 (and maybe also FF4) for me. FF5's gameplay is *much* better than FF4's and FF6's; it has character customization unlike FF4 (basically, in FF4 the game chooses your party, but in FF5 you get to choose), and it lacks many of the flaws found in FF6 (FF5 is less cutscene heavy and *significantly* better balanced while providing a much bigger set of strategically significant combat options).

(I note that I didn't play FF5 until *after* playing FF6, because FF5 did not see a SNES release (it only saw a Japanese SFC release).)

C & C 4 killed me playing c & C games for years after playing that train wreck iet sucked out all the fun off an rts and made me stop playing those games for quite sometime.

I'll get round to Swat 4 someday, after I somehow manage to finish 3. That final level is insane. Just can't take out the guys in the control tower :P

Dune 2 is almost completely unplayable for me in its original state, precisely because of the lack of drag select. But the modern reverse-engineered versions with drag select and higher resolutions are still very enjoyable for me. Only problem is that they tend to alter things I'd rather have stay the same: like the AI and the construction menu with its awesome artwork.

I...actually kind of agree with that. (FF5 was the first FF I played)

In terms of gameplay, FF5 ranks near the top of the series due to the sheer amount of options you have and the fact that practically every boss has a conventional way to beat it as well as a quick-and-dirty way that requires an overspecialized party taking advantage of one or two obscure weaknesses. It also helped that your options grew as the game went on, compared to FF6 where the diversity of your team actually went down as your characters worked their way up the spell lists and many character-specific skills started getting outdated.

FF5's story and characters are still extremely silly though.

I don't think it ever happen for me. I can still enjoy games which were completely overshadowed by their successors like first installments of Warcraft, Settlers or HoMM series. Sometimes I have a feeling that one game may ruin some aspect in other similar games. For example I used to be quite excited about heroes leveling up in Tzar or Warcraft III but after playing Warlords Battlecry and especially Warlords Battlecry II I think hero leveling system is meh in 95% RTS games. If you don't know what I'm talking about go and play Warlords Battlecry II and experience the ultimate hero customization :)