I recently discovered the Nintendo DSi and I must admit that I have a lot of great time playing with it! But I wasn't really excited by this little piece of hardware at first glance!
I didn't really like the fact that the DSi had a very small screen (only 3.25 inches with the possibility to display only 260 000 colors) and low resolution graphics (unlike the PSP for example).
But the touch screen really makes the difference! And I must admit that Nintendo as quite a game library for all ages! My kids and my girlfriend are even using it more than I do!
Some of the features are a little useless in my opinion (like the digital camera... who will play with it for more than 5 minutes?).
But the great amount of interactivity makes up for it (the touch screen, the fact that some games are also using the microphone for another level of interaction with the user!).
I don't have what it takes to fully take advantage of the wireless capabilities (my router is wired) but I'm still enjoying playing games
like Mario Party or Professor Layton and the Curious Village! I might also try games like GTA Chinatown wars in a near future.
The bottom line is simple: I think that Nintendo is heading in the right direction with the Nintendo DSi and the Wii. Of course, graphics are pretty poor on a Wii compare to an Xbox360 or a PS3, but the concept is promising can only get better with time.
Will Microsoft or Sony follow the same path one day? Maybe, maybe not. But one thing is sure: interactivity is the key (just look at the success of the Guitar Hero and Rock Band franchises). Using a simple joystick is not enough anymore!