Thanks to Membrans Sound Design for linking to Recordinghacks; that's how I found this.
The original question is from about 10 months ago, but in case anyone is still looking, I can point to some specific resources. In all these cases, we did exactly what the OP requests -- same material, same mic position, same signal path. For many of these, you can listen blind right on the website. We have WAV downloads for most of them too.
We put 30 different ribbon mics through 5 sessions: guitar cab, alto sax, acoustic guitar, character voices, and drum overheads. This was probably the biggest ribbon-mic test in history:
In a feature called "the ultimate podcasting mic shootout," we collected every great broadcast dynamic mic and tested them on voice: MD-421, RE20, SM7B, PR40, and more.
Professional voice actor Mark Keller tested two rounds of high-end condensers: Neumann, Bock Audio, Manley Labs, sE Electronics, MXL. There are HD videos for these, too:
Here are six popular LDCs on two acoustic guitars:
One of our most recent features lets you hear seven (or nine) popular sub-$200 condensers on sung vocals, acoustic guitar, guitar cab, and voiceover/podcasting.
In short, we do this sort of thing all the time. I won't pretend that it's as good as having all these mics in your own studio for a weekend, but we do the best we can to make these tests useful and educational, such as including popular reference mics whenever possible.