I know this term usually applies to CGI that is close to being real, but not close enough, so the mind sorta repels from it and finds it creepy, but I've another personal use for this term.
There was that period in games history when 3d came in and gradually became the norm. We all remember it, and how people trying to jump onto this bandwagon sometimes ruined their product, or moved way ahead of the pack.
To me, that period in gaming history that just hasn't aged well at all for the most part. Up until the early 00's infact.
Alot of the time I really struggle to play games from this Era. Original half-life for example. I don't really know why but I find the games aesthetics really lower my enjoyment.
What is your gaming Uncanny Alley in terms of time period. Do you even have one? Are there specific games whose looks just put you off for reasons you are, or are not just not sure of.

I'm not sure what you mean, I've heard of the term uncanny valley, which is the bridge between graphics and real life, saying that sometimes the graphics on something will be so good, you'll know it's computer generated..

well the term is uncanny valley, but I get what you mean. However...if you are saying that graphics keep you from enjoying a game, you are probably on the wrong site, heh. I honestly find some of the "newer" graphcis to be rather annoying - especially the whole "Let's take a character model in CGI and make him look like he/she is wrapped in cellophane." Look you see in so many new games. Game designers tend to soften that look a bit but adding clothes, armore, weapons, etc....but it is still there.
if a game has fun play mechanics, the graphics could be Squares and lines and I'd still enjoy it. Sure I do like good graphics, but to me that isn't always equated with "new" graphics.
Take Planescape: Torment for example, one of the games that would be in the OP's bad graphic era...yet it is so beautifully designed and everhthing just looks so detailed... The resolution isn't what we have now, but man the way the game looks along with the play mechanics and the story? That is a game any gamer should try out, imho.
So graphics have a bit to do with the experiance for me, but not in the way most people think. Just because something is new does not make it better.

I remember this time and many "Classics" of the beginning of the 3D-Era did absolutely not age well. Often the Idea or Concept of a Character was brilliant, but then the technical Limitations were just too big. Look at Half-Life, still brilliant Games, but very hard to look at, Return to Castle Wolfenstein, great Game, technical Limitations just make it unpleasant. On the other Hand there are Games in 2d that even today are brilliant, 2d Fighting Games are a good example, Street Fighter or The King of Fighters Series, 2d Shooters like Metal Slug, old School RPGs like Baldurs Gate or Planescape STILL play great, a big part of this playability is their great graphical Style.
I still love good old games, but it is IMO undeniable that Graphics that did not age well take away much of the fun.

I don't know what your guys hangups are, but I can still enjoy Half-Life 1, and Return to Castle Wolfenstien just fine. You guys are caught up too much in appearances. I still play Hexen, Sin, Quake 2, Doom 1 &2 (and skulltag multiplayer wads), I mean.. even Spear of Destiny.. I don't understand what the hang up is on those games, sure they're old, but I take them for what they are.

I can appreciate the art design in Ultima V, which I think looks nice, or Baldur's Gate 2, which I think looks better than many 3D games, or Bioshock.
Some games were pushed into being 3D even if that was difficult or didn't suit them, Neverwinter Nights for example doesn't look anywhere near as good as Baldurs Gate 2, despite its 3D engine, but I like both games and have played them several times.
Other games were born for 3D, such as flight sims and space shooters, where a 3D environment can get the most use.
As for the uncanny valley, as we get ever closer to being able to replicate human faces in computer games, the more the little details matter. In Final Fantasy IV, you accept that a small collection of pixels is a person, but now, if you see hair that doesn't move with the wind, or blank, dead eyes, you think there's something wrong with it.
I suppose it's a little bit of the minds eye, we're quite happy adding our own details to something, like seeing faces in a cloud.

I agree. The only old 3D games I have problems with, are ones that should never have been 3D in the first place. Take Simon The Sorcerer 3D for instance.

Uncanny alley... sounds seedy. I bet that's where all the cyber nudity's at.

I'm not raging against aged graphics, as such. I think lure of the temptress and beneath a steel sky look fine, they are pixel art basically.
I think the old fallouts look great and sacrifice and many of the other games I've got here I don't mind.
But there are games where the polycounts to low, or the textures too muddy or...something. They were great looking in the day, but due to uninteresting art direction, just haven't aged well.

I do but I'll get banned if I show you here. Meet me at the uncanny underground parking lot after dark.

It has been an issue a couple of years ago. Doom 3 is a bright example of that. But in the more recent games I don't see the problem any more. It seems like developers finally learned to avoid the issue of characters looking like plastic action figurines.

If the rest of the game is made to look like plastic action figurines, then it's cool because it's the artistic style. :)

Unless its unintentional. In which case its not only cool but also hilarious.

Strange.
I'd rather play a game with well drawn and animated sprites than something from the current generation. A game with a unique visual style (Okami) is more fun to look at than some modern high-resolution game that looks great but is set in some dingy grey and brown environment (Gears of War).