I agree with you that there is a notion that the best pictures come from the latest and greatest equipment. Watch any chain store commercial advertising a camera and the main selling point is always how many mega pixels it has. More mega pixels meant better photographs - or at least that's the angle pushed by the manufacturers. Tell a layman that the D3s with its 12mp sensor is about 4 times more expensive than then 16MP D7000 and they'd walk away scratching their head. I think its this type of marketing that has given people the misconception that anything but the latest technology is redundant.
Newcomers are also seemingly ignorant of the hundred plus years worth of fantastic photographs that have come before todays offerings. Give a complete novice a £5k camera and lens, and a pro a £500 camera the results will invariably be far, far superior from the professional. The most expensive doesn't automatically equate to the best photograph. At the end of the day, the camera is just a tool. It is down to the user to create something with it.
Digital SLRs today can still not come anywhere near the level resolutions of say an old 8x10" plate camera. Some of the most impressive landscapes/seascapes I've seen have come from an old plate camera. The level of detail and overall image quality were immense. This is where the technical and creative abilities of the photographer are absolutely paramount, as well as the skills needed to develop the image in a darkroom, which is another art in itself.
For the majority of photographers, I'd go so far as to say that the now lowly D40, is as good as any person really needs. In average daylight conditions with optimal ISO, you're not going to see a huge difference in image quality from a D40 to a D3 (aside from image size).
Its when you step into the realms of low light/ high ISO that having a camera with those sensor capabilities can make the difference between getting the shot you want and it being lost through motion blur, under exposure or digital noise. Don't get me wrong, the photograph is only ever as good as the photographer but, there becomes a point that the creative ability of the photographer is negated by the inability of the hardware used to capture the image.
I have the D90. Its a great camera and does everything I need it for. However, I do find the noise capabilities a limiting factor for natural light portraiture. Not so much an issue if shooting in monochrome as it can create a film grain quality. For colour shots, the noise is definitely a problem once you get above 800-1000 ISO.
Ultimately, it all depends what people want the camera for and its intended use. Landscapes, ideally you want a large resolution camera, particularly if you print the images for wall art or canvases. Likewise for work in the studio, hence your D3x and Pentax 645. If you're into natural light portraiture or concert photography, then the newer DSLR's with advanced low light capabilities are certainly the best bet. The D7000 does very well in this area, especially for an APS-C camera. If photography is your profession, then like any craftsman, you want the best tools for the job, that deliver the goods and allow you the flexibility and precision that is often required. The full frame cameras provide this.
There is definitely a tendency for overkill and purchase equipment that you will never use to its fullest. Again this comes back to the science of marketing, in convincing people THEY MUST HAVE the latest gadgets. This week I had a conversation with a friend about the latest "Dr Dre" headphones. Hyped up to be the bees knees and selling for the bargain price of a mere £280! "They're like studio quality, man! You can hear everything" I was told. I replied, "I'm sure they are and I'm sure you can but, you and 99.9% of the idiots who buy them will be listening to MP3's...... which is a compressed audio format."
As the old saying goes, a fool and his money are soon parted - although I confess I still play the lottery in the infinitesimally small chance that "it could be me". Unfortunately, the finger I seem to get pointed at me - is the middle one