Welcome to the forum...
Quote: You are NOT gaining resolution. You are simply losing field-of-view.
Consider a 24 MP APS_c compared to a 24 MP Full frame. Within the area of the crop sensor, on the FF it's about 11 MP, on the APS-c it's 24 MP. You are gaining a pile of resolution if your subject lies within the cropped area.
Or consider an image where you have a 250mm on crop where 24 MP fills the frame. On a 24 MP FF sensor, you need a 400mm lens to get the same field of view and resolution...
Are you starting to get the hang of it?
Even on a D800 the area of the crop sensor is about the same a K-5. For the area inside the crop sensor you still gain 400/lw/ph using a K-3. So you get more effective magnification based on the smaller pixel size.
In other words, if you're shooting macro.. both with say a Sigma 70 macro, you get way more magnification inside the area of the crop. magnification in the sensor if you shoot both from the same distance. You only maintain resolution equality if you have a 1.5x longer lens on the FF. And that's what the crop factor is about. On two 24 MP cameras. shooting from the same position you'd need a 105 macro, to give you the same FoV as you'd get on the 70 with the APS-c camera.
It's all about what you see through the lens. Try it, you'll see it.