So make it a dog/cat analogy. I'll gladly concede that it's a much better fit.
The point still stands.
I am not sure I get the point, either.
I can only assume people played D&D 3E because it gave them what they individually wanted. Now D&D 4E gives some people still what they want (and some people more then 3E did give them) and others not what they wanted (or at least less of it.)
Is the best analogy that people had a dog, and some people liked it because of the fur, but would like to to purr when petted, while others enjoyed walking their dog? But can we follow that the dog owners got it right - it was a dog, so the pet shop should still sell dogs to them and not switch to cats? Or does it just mean that a cat is also a valid pet and the pet shop should sell those too? (The analogy fails the moment we consider that a real pet shop would sell you both cats and dogs - well, assuming they are sold in pet shops.) Or do you think D&D always stood for dogs, and when the "Dog Shop" suddenly sells cats he's doing it wrong?
But again, the problem is that it is every easy to distinguish between cat and dog. People usually know that they have a cat or a dog. But people don't necessarily distinguish exactly what makes a particular game they like "their" game - until you change the game and remove the parts they liked.
Nah, this analogy just sucks. It simplifies the aspect that is exactly not simple and creates the problem we are talking about! I think food analogies like "spaghetti sauce" can work better. D&D is a spaghetti sauce. But do you like the sauce because of the chunky parts, or because of a particular ingredient, or a mix of things? You'll only find out if you still like it if I change some of the ingredients.
Or if it has to be cats and dogs, D&D is a dog. D&D 3E and 4E are both dogs, but different types - maybe one is a sheppard dog and the other is a Chihuahua, and the Chihuahua showed you how much more you liked big dogs over small dogs, or how much easier it is with a small dog in your apartment...
[/rambling]