There were a few other points they all had in common.
"N64-level graphics" was an early one. The exact ancient technology varied a little, and it may sometimes have been an ancient game, but the comparison itself was quite consistent.
Also read something about Playstation 2 graphics. Both N64 and PS2 had their focus on other features than texture size so this might be the reason for people coming up with that comparison even if graphics in general have advanced tremendously since then.
The usual reception seems to be -> Lower texture resolution than some other game: N64 or PS2 graphics!
Looks like the texture resolution is considered to be a very important factor in game graphics. So important that everything else comes second.
Needless to say that people should reconnect their old consoles to their tv and have a real look at what they're talking about.
N64 games look like total crap in comparison with modern graphics. Even when running on a pc emulator with higher screen resolution.
"Megatexture = megafail(ure)" used to happen quite a lot.
Posting screenshots of relatively open Doom 3 scenes compared to Rage with your face rammed into a wall, and then trying to use them as some kind of evidence that it's a step backwards, was common shortly after release.
As was posting screenshots of a sikkmodded Doom 3 and trying to use that as evidence of the same.
This might be more important when it comes to someone trying to decry a competitors product.
Especially the comparison with Doom3 with installed highres mod isn't remotely fair. The original Doom3 had fairly low texture resolution, even at the time it was released. And it's texture resolution is definitely lower than Rage's.
I recall reading a post by Carmack in conjunction with Doom3's release where he stated that he tried to achive high res visuals just by rasing screen resolution so objects in the distance look crisp and sharp. This maybe a personal preference or a limit to what OpenGL can do with texture blending when using detail textures when getting up close to an object like the Unreal engine does in perfection for example.
In fact, i can't recall any OpenGL game ever having this feature.
The whole "John Carmack is a washed-up has-been who is out of touch with modern ideas" thing is, interestingly, not new. I've been going through old usenet archives recently for some research, and came across occurrances of it dating back to at least as early as 1998. At the height of the OpenGL/Direct3D wars it was reasonably common for a Direct3D evangelist or two to pop up and come out with that one.
Maybe Microsoft is still trying to get rid of the competition.

Although this competition doesn't really exist anymore. Someone should tell them.
Btw.: I personally preferred DirectX over OpenGL when i started prgramming as i found it easier to get started. DirectX gave me the complete package including all docs in one download. That's all.
I never considered OpenGL to be inferior when it comes to rendering graphics.