...players are able to surpass what they have done, simply with mods? Let's take for example TES: Oblivion and Crysis.

In Bethesda's RPG, players have released numerous mods that enhance the visuals, notably by adding sun glare, doubling the textures' resolution, or improving spell effects.

Crytek's critically aclaimed FPS has known a significant improvement in the visual department, merely with edited notepad files. By changing a digit here and there, vast ameliorations have been made: Take a look at these screenshots with mods

http://www.incrysis.com/index.php?option=com_content&task=view&id=768.

Should developpers feel ashamed, or on the other hand, feel proud of the gaming community?

I don't know if most gaming sites follow this method, but in the case of Gamespot for example, the credibility of a lot of reviews depends on the reviewer. This is why when one relies on reviews to purchase a game or not, he should take in account the reviews of multiple sites.

Most gamers care about Gamespot, Gametrailers, and IGN for reviews. That doesn't mean other sites are bad: they are just less well-known.