The "games as art" discussion is stupid. IMO if you're arguing "can X be art" with any "X", then you're just a wanker. You should be instead be asking people "what does X mean to you", and you know, listening to people's feelings, because that's what art's about. Of course "X" can be art to some specific beholder of "X". Put down the red wine!
Anyway, the art debate doesn't really have much to do with why people hate on "the idea guy".
People hate on the idea guy, because an initial idea is nothing by itself. A game designer doesn't write down an initial idea, put it in an envelope and wait for it to be made. Designing a game is a collaboration between everyone involved. The designer, the programmers, the artists, the animators, the audio staff and the business managers all work together as a multi-disciplined team. As with all art, you often have to work within constraints. The programmers and businessmen are often the ones that will be dictating constraints to the designers and artists, who then have to work within that space. Also, programmers may unexpectedly defeat constrains, and open up new avenues to design within. Actually, every department is dictating contraints/requirements/limitations/possibilities to every other department, and reacting to the options they're given.
The people that do this kind of design work are real world game designers.
The guys that write up their poorly thought out mash-ups of other games, or their clichéd storylines with no information on actual game mechanics, and then complain that they can't get their games made -- these are the guys that people call "idea guys", and make fun of.
This just leaves one more question, when it comes to making games, who is the painter? Well, that would be the game designer. Because as people have argued before me, game designing is a skill set and I will say more even, it is the only one truly essential to the quality of games.
It totally depends on the level of detail in the initial design, and the ongoing involvement of the designer to reshape his initial design during it's implementation as issues and opportunities arise. This is a creative process that involves input from both the designer and the implementors. Both of them are just as important in creating a wonderful bit of art as a result. If you've got a great designer and bad implementors, you're probably going to put out worse art that a team with a bad designer but great implementors.
Saying the designer is the painter (and thus, the "real artist") is like saying that the guy who said "Hey Rembrandt, you should paint Jesus calming a storm!" is actually the real artist and Rembrandt is just the technical implementor, not worthy of mention.
Yes, design is a real skill set, which is why most games companies will have a few on their payroll. However, it's not their initial ideas that make them valuable, it's their skill at being a guiding hand throughout the entire development of the game that makes them valuable.
Your stereotypical idea guy does not possess this skill set, or any skill set really. The stereotypical idea guy actually has bad ideas that he thinks are good which is why it's such a fun stereotype to make fun of.
If the game designer is the painter, the 3d modeler, animator or 2d artist might be the manufacturer of the paint. And the programmers can be the one who made the canvas the painter is using.
No, that metaphor completely misses the point that the interaction between designers, programmers and artists are all two-way interactions. The artists and programmers, the artists and designers, and the designers and programmers, all supply work to each other and feed off each other. All those relationships are reactive and dependent on each other.
For this metaphor, you'd need the painter to require some specific kind of paint and canvas that don't yet exist, and his art to be an iterative process that requires a search for both the final painted image that he's after, and a search to develop the kinds of paints/canvasses that will allow this image to be created. This journey would likely change directions at different points as certain limitations in the search for paint/canvas are decided upon. All of this R&D is also costing money, so all the artisans involved must balance the amount of time they spend on each area with the value that it will bring to the artistic vision, which is where project management comes in (which is often another skill that good game designers are expected to be trained in, but the stereotypical idea guy lacks).