I'm new, and I'm also from the camera world and though many people will say "it all comes down to glass", that's only true when you're pixel peeping. In all honesty, most non-photogs will not notice the quality that different glass can do! What glass will help with is the chromatic aberrations, vignetting, and sharpness (when you've blown the picture up 100%). Of course, other things such as barrel distortion is also controlled by a quality lens when you are at your wide end. And if you guys also really know, lens can help with light diffraction occurring on the sensor -- This translates to lens resolution (This talks about light intensity -- controlled by the aperture of the lens).
What really matters and how the image looks is mostly dependent on the sensor itself, just like the old film days. The sensor can be considered the "film" of the camera, as that's exactly what it replaces. The memory card just stores the images of what the sensor takes. The sensor determines the contrast, the color reproduction, the dynamic range, the amount of grain, etc. I've talked about diffraction earlier, and the sensor size can also have "diffraction" occur when the pixel density is too high. If we think about each pixel on the sensor (in this case the Droid Incredible being 8MP, and the Moto Droid being 5MP) as buckets, then we can better understand the concept of digital photography. So the bigger the buckets, the more detail information you can hold. However, in contrast with pixel density, the higher the resolution (higher MP), the bigger the print you can make, the bigger the picture will show up on your screen! In fact, I think the biggest SCREEN resolution I've seen is approximately 4MP (2560x1600 @ 30") so your motodroid's resolution is still higher than the biggest PC monitor available to us!
I'm guessing the moto droid and the htc droid incredible's sensor size is the same. If that's the case, the motodroid have more potential to crank out better detail than the HTC droid incredible, but if they put a sensor that's worse than the droid incredible, then that makes ALL the difference. Plus it helps when there's the app where you can mess with your image!