Business 2.0 recently took an admittedly short stab at what makes the Nintendo DS a winning proposition over Sony's PlayStation Portable. That they came up with Nintendogs is no surprise, of course.
Quoting Japanese sales figures and lamenting the dearth of readily available US sales figures, they then offer their take on what makes the Nintendo DS the platform for the virtual pups, noting its networking capabilities via Bark Mode, intuitive touch-screen interface providing simplicity, and of course the capability to directly "touch" your dog, offering emotional bonding far beyond what Tamagotchi ever could.