hedwards: I'm not so sure you can really separate the two in such a manner. Much of the hinting and hand holding that goes on in the game goes directly back to the graphic design elements which are tied intimately to the aesthetic values of the game.
Yeah, it's a somewhat complicated matter which is not discussed enough in my opinion. In academic circles the field of game design focuses on the mechanics though - as Raph Koster puts it: game design is solely about abstract formal systems. Such a clear distinction between the different fields and professions is useful and even necessary. But as you noted, the proper interplay between the different aspects is important - and I think respecting the different professions while embracing the whole medium is one of the biggest problems the industry has. You don't want to know what the M.O. of some of the biggest and most successful companies looks like...
Once I actually approached the lead game designer of a certain popular cRPG - he was introduced to us as the main guy behind the game. After others were done with their traditional ass kissing I instantly told him that I'm not a big fan of their game, noted how already their interface keeps the game from being better than average due to not being at all adjusted to their mechanics (it was in fact taken directly from another famous cRPG including all its flaws). He welcomed my constructive criticism but responded "yeah, we have no say in that - the interface department is responsible for that". I think that little anecdote perfectly explains how the industry tends to handle the different fields and how even big companies have problems dealing with that.
hedwards: It surprises me a bit that the books cover aesthetics, because a huge number of games get it wrong, and they age much more quickly as a result.
Agreed but note that the people who write these books or hold lectures are not the average guy form their profession. The fact alone that they write educational works about their field or teach means that they give an exceptional amount of thought to it. The average designer/artist is just trying to get his job done, because of numerous other factors he may not even have the time or capabilities to include some sophisticated artistic approach in his work. As one artist from the industry put it: "we are craftsmen, not artists". That approach does get the job done but results in the problems you noted.
It's natural to assume that shortcomings in the aesthetic value of, say, a game's level design are mainly caused by the lacking artistic skills of the designer but with the industry's usual constraints even a very sophisticated level designer with high artistic skills may not be able to go for anything else than "functional".
