Those are (high res emulator shots of) actual DS games, which was a platform with relatively similar technical limitations (in terms of polycount and texture variety) to the PS1/N64, but implemented without some of the major flaws of those consoles, and coded to by devs with much more experience at working in 3D.
Late-gen PS1 stuff isn't that too dissimilar, aside from the unavoidable technical limitations of the platform.
That's pretty much exactly the quality level that people are talking about when they discuss this subject (although personally, I still think that low-res rendering has a certain charm to it).
DS isn't a "retro" system. The idea presented in the topic is N64/PSX era as a target asthetic for new retro inspired games -- which I think is a terrible idea. Whether DS games look good (some do, sure) is another topic all together. PSX and N64 represented, in my opinion, an era when games were, more often than not, hideous to look at.
I'm curious Jobbs – I agree that all first generation of 3D consoles (PS1/N64/Saturn) had issues – but what about arcade and PC? What do you think of Model2 arcade games and early software rendered PC stuff like Quake1/2 or Homeworld?
Also, Metroid didn't look like that either on an actual screen. The aspect ratio isn't even correct in those shots you posted earlier.
In general I am not a fan of most any early 3D -- I think the form went through severe growing pains and didn't become particularly tolerable until the XB360 era (I know a lot will disagree with me, but even during the gamecube era I found the games sort of ugly for the most part, and played now I find them intolerable -- whereas I can and do still play SNES). N64 and PSX are 3D at its worst, though.
I recognize not everyone will agree with me on these points. Re. The Super Metroid screens, I just did a quick google search and grabbed some. Suffice it to say, I know what the game looks like. Five feet away from me right now there's a 27 inch CRT with a Super Nintendo hooked up and Super Metroid in the cartridge slot.