C'mon, man. You were there. You remember people fighting for the PS2. You remember people not being able to get it for months (Like me--I couldn't get mine until March of the next year!). You remember people camping out for the Xbox 360. You remember that, at the time, the Dreamcast was the biggest single day money maker of all time (Google it!). You know how hard it was to get our hands on my hot, throbbing Wii.
We expect these results because we've seen these results. Maybe the heat dies off quickly after the initial boom but we expect a new device to be met with some demand. The DS was an unproven commodity at the time. We didn't know what to make of it. The PSP was Sony's first foray into handheld gaming. Again, it had to prove itself. The other consoles had hype and legacy backing them up. That's why I was shocked to see that the 3DS wasn't selling. It had the hype. It had the legacy. It had some awesome features. I expected it to fly off of shelves. Now, with the PSV, it performed about as well as I expected. It lacks "newness".
Also, think about the failed consoles in history (I guess the Dreamcast can be included though it did sell pretty well in its two years--just not well enough to save Sega). You can normally tell right off the bat if it will be a runaway success. With our unknown consoles of tomorrow (Wii U, Xbox Infinity, and PS4), we want to know which console will be the "standard bearer". We all want it to be our console of choice and we all believe in our favorite brand. We expect them to do well, too. That's why PS fans expected the PS3 to jump ahead of the Wii and 360 right out of the gate. When it doesn't happen, it's hard to accept.
Reality and expectations are two different things. If you don't believe me, ask some of my ex-girlfriends.