That's where I personally think the sadness begins. People don't want subtle innovations that develop over time, or basic improvements to a device. They just want something they've never seen before that has a short-term "wow" factor to attract the overpaid and underintelligent. Like them or not, gimmicks are what attract attention and what get press. Such as WiiFit... that sold a ton of Wii's, regardless of how often they are currently used.
The 3DS, the Move, and Natal are all just designed to attract people who like to be more interactive with their experiences. The standard 2D, controller-based interface isn't enough any more to hold some consumers' attention. Of course, all these ideas have been done before, and all have failed in the past. Remember the Virtual Boy? Granted, it is different in certain ways, such as it actually supports more than 2 colors and you don't have to stick your face in the device, but the general principle is the same. Sega had a camera-based movement system called the Activator, if you can recall. If you look it up on YouTube, I believe you can still find the old commercials for it, it was actually pretty funny. But all this has been done before, they are just applying old technology with new innovations. Thankfully, most of the bugs from the previous versions have been worked out, but still they are just gimmicks. Probably the oldest example I can think of regarding motion control would be the Power Glove, and we all know how bad that sucked.
I have a DS Lite (as I couldn't see the point in buying a DSi since I already owned the Lite), and while some games do make use of the touch pad, not a lot use it well. Games that solely depend on the use of the touch pad for every function seem stupid to me. The better execution of the touch pad I felt was in GTA: Chinatown Wars. It was more like using the touch pad to manage inventory, and kept it as a secondary input instead of the primary. Why bother having a control pad and buttons if you just want me to stab a screen with a plastic stick?
I haven't had a chance to experiment with a Wii, so I can't really speak as to how well the motion tracking works. Some games use it well, others not so much. But those are the breaks. You've got to try things out to see how they'll work, and sometimes you just get too heavily invested in a project to return to the R&D phase if something doesn't work exactly right. If it weren't for the bad examples, we wouldn't enjoy the good ones.
3D tech, while gimmicky, does appear to be the way of the future. Since I saw the first 3D tvs on sale a year ago, I thought it would just be a matter of time before it would become the possible standard. Thankfully, nothing has had the impact that DVD technology did when it launched. Quietly at first, but soon you couldn't even rent VHS tapes anywhere. And look at Blu-Ray... the PS3 is still the only console that is using this tech. Possibly the 360 will have an add-on in the future after Natal comes out, but I highly doubt that MS will convert over to making games on Blu-Ray discs. Look at how many people still use DVDs... Blu-rays are still too expensive for most people. I don't even know anyone who has a stand-alone Blu-Ray player, they just use their PS3 (provided it hasn't quit on them). Even the first Blu-Ray movies that came out people complained they looked worse than DVDs.
Given enough time to work the bugs out, these gimmicks will eventually become common-place. A excellent example I can think of is the scene in Back to the Future 2 when Marty McFly is playing Wild Gunman with a light gun, and the kids made fun of him for playing a video game where you had to use your hands, "like a baby toy". Granted, we don't have hover-boards or self-lacing shoes, but apparently hands-free video gaming in the third dimension is quite a possibility.