You actually can rate games you haven't bought.

I stand corrected. You're absolutely right. I just hadn't scrolled further down on the game description screen.
Still, I doubt many people do that, with games they don't like.

You never know particularily with the way some people randomly rate posts neg. or pos. depending of whichever makes the least amount of sense.

I'd agree that there seem to be a lot of old games people give a free pass because of nostalgia or because it's considered a "classic" game.
Nostalga also plays a big role. I will always have a special place for Commander Keen 4 and Sonic the Hedgehog 2 because they were the first games I played on the PC and Sega Genesis (My first console) respectively.
Don't get me wrong, I still think both are great games, but there's a lot of other games I played as a kid and though were awesome and then went back only to realize that as an adult and 10 years later they just didn't hold up.
Yet do we rate down a game just because it is archaic and outdated when compared to cutting edge PC rigs and Hot new consoles? I think not. Some games are going to be remembered as classics because they were groundbreaking at the time but other games will be criticized for being rudimentary in retrospect and yet still be great games. I still go back and play Marathon every now and again because even though it's a simply and crude FPS now it's still fun.
On the other hand there are games like Mario 64 that I don't think are all that great now. Sure, it was groundbreaking at the time and I remember playing it when it first came out and thinking it was amazing, but now it just strikes me as not as solid or as fun as I remembered it to be. Granted, I still think it's a good game but I don't think it's a "classic."

at the same time there are great games that helped to revolutionize the industry, however they are unplayable today, for example Goldeneye. Great game, but doesn't hold up to todays standards.

It's true that the Super Nes remake is superior, however did the remake have as much of an impact as the original did?
No.

That's the thing though isn't it? Mot games are rehashes of games done previously. Half Life, Super Mario, Call of Duty etc all have huge followings coming from the huge arrival on the scene.
Call of Duty, for example, was the first game to have a proper, gob smacking cinematic opening, well....apart from Homeworld, that was a cracker of an opening sequence as well.

As long as we're on the subject of really old games, allow me to give honorable mention to a true classic that I still play occasionally to this day: Wizball, for the Commodore 64.
This game had it all: originality, great innovative gameplay, graphics and sound that just fit perfectly, and of course a brilliant soundtrack by Martin Galway.
Wizball is an example that superior technology does not always make superior games. Most people agree that the C64 version of the game was undeniably the best. Much better than versions for other, arguably much more advanced platforms, like the Amiga.
As I said, I still play it. These days on emulators, of course. And I, for one, still think it's as fun today as it was back then. Oh, and "back then" is really "back then". The game was released in 1987.

If you're going down that route then there's Manic Miner and Jet Set Willy, which were fab games hailing back to 1983!! Oh God!!
The music would drive you insane after a while with the same tunes over and over again.

I was born in 1987..
Sorry to go off topic there.
Anyway, if a game doesn't affect history, regardless of which is better, only one deserves to be noteworthy.
Many people have said on my Goldeneye Youtube video, that Quantom of Solace is a much better shooter, and I'll admit it most likely is a much better shooter, but Goldeneye helped to fix up the FPS on console genre. Without Goldeneye we wouldn't have Halo or Quantom Of Solace on consoles. So while yes, Quantom of Solace is probably a much better game to play, with refined game play, it ultimately boils down to being just another FPS shooter on Xbox or PS3 or PC, nothing truly remarkable, while Goldeneye reinvigorated the console FPS genre.

IIRC wasn't Goldeneye the first shooter for the consoles, ever? T'was a good game but is bettered by most these days.

Edit: I totally screwed up this post. Just negative it please.

Nope, there was Wolfenstein3D and I think Doom even, on SNES. However Goldeneye really put a fevor in showing how successful a FPS on the console can be with the right dynamics.

Half-life, half-life, half-life. If you don't have the wow factor of scripted events being new and sexy, its a pedantic, lifeless shooter with outdated graphics to boot.
Doom on the other hand, is still a blast, and if anything has benefited from developers collectively deciding "KILL 'EM ALL!" isn't a sophisticated enough concept.