Good lord, man.  I think the original Gameboy had a larger color pallet than that.   Joking aside, it does belong on the list anyway.

Resistance 2 and MGS IV are solid choices too.

Killzone 2 misses this list by less than 2 months. 

You tout objectivity but saying "best graphics" is defined by technical effects only is drenched in subjectivity. Where did you get this definition from? The term "graphics" merely refers to the images on the screen. That includes the technical effects, but obviously the art direction, use of colors, framerate, image quality, creativity, etc. as well. Prefering the graphics of, say, Muramasa or Klonoa over Gears of War is perfectly fine. There is no such thing as "objectively better graphics." Otherwise this thread would serve no purpose. Make your own thread discussing games utilizing most FLOPS or something instead.

OT: my favorite visuals of early last gen are probably Bioshock, Halo 3, Metroid Prime 3, Super Mario Galaxy and Geometry Wars.

Nah.
The visual rendering pipeline that Crysis outputs was a step ahead of all those games you listed... And the reason why graphics isn't subjective but art is... Is actually simple...

Art is the artistic approach to building a scene... Just like a painting. - And people will prefer different art pieces.
Graphics is the approach that frames the art, the types of brush strokes, paint used and so on, that can help define how a piece of art will fundamentally look.

A game like Crysis was pushing graphics effects that no other game was, it had screen space ambient occlusion, it had ray-marched volumetric lighting, parallax occlusion mapping, gaussian depth of field, per-object motion blur and so much more that made that game a graphical showpiece like no other at the time.

Bioshock ran and leveraged what Unreal 3 was outputting, but did have some great graphics effects, especially in the water department. - But it still wasn't Crysis.
Halo 3 had HDR lighting, Tessellated Water effects... But again. Still not Crysis.
Metroid Prime 3 and Super Mario Galaxy when compared against other games released on other platforms only had Art to push (Although had relatively impressive levels of geometric complexity thanks to intelligent culling), because the console that those games were released on, just weren't capable from a graphics effects perspective, you couldn't have global illumination for instance.

Nah.
The visual rendering pipeline that Crysis outputs was a step ahead of all those games you listed... And the reason why graphics isn't subjective but art is... Is actually simple...

Art is the artistic approach to building a scene... Just like a painting. - And people will prefer different art pieces.
Graphics is the approach that frames the art, the types of brush strokes, paint used and so on, that can help define how a piece of art will fundamentally look.

A game like Crysis was pushing graphics effects that no other game was, it had screen space ambient occlusion, it had ray-marched volumetric lighting, parallax occlusion mapping, gaussian depth of field, per-object motion blur and so much more that made that game a graphical showpiece like no other at the time.

Bioshock ran and leveraged what Unreal 3 was outputting, but did have some great graphics effects, especially in the water department. - But it still wasn't Crysis.
Halo 3 had HDR lighting, Tessellated Water effects... But again. Still not Crysis.
Metroid Prime 3 and Super Mario Galaxy when compared against other games released on other platforms only had Art to push (Although had relatively impressive levels of geometric complexity thanks to intelligent culling), because the console that those games were released on, just weren't capable from a graphics effects perspective, you couldn't have global illumination for instance.