One point I didn't see mentioned... the Wii will likely gain an even higher percentage of dominant 1st-party titles--over its lifetime--compared to the other two current-gen consoles.
Why? The difference between PS3/360 and Wii is more pronounced when it comes to development, as opposed to comparing development between PS3 and 360 (excluding games that take advantage of the custom hardware in either of those systems). Take a look at how few cross platform titles have come and are coming to Wii. A developer can build an Oblivion or GTA4 and create similar graphics for both. Porting to the Wii requires a downgrade of the graphics or building to the Wii as the lowest common denominator. Some here might say that all it takes is a simple graphic filter to downgrade the graphics, but there is a little more to it than that (I've worked with graphics and done software development for 26 years and that has been my experience). There is also the issue of horsepower... can a game that has a lot of AI, etc. run as well on the Wii as on the 360/PS3 which have more powerful CPUs?
Some companies will be willing to go the extra mile, but for others they will decide not to port to Wii due to the extra cost or the need to reduce the experience. Other companies won't port but will decide that an entirely new game will need to be developed for Wii (The Force Unleashed is an example). And if a company ports to the Wii, they will need to make their port better in novel ways, such as excellent use of the Wiimote, to get multi-current-gen-console owners to buy the Wii version vs the PS3/360 version. In our household we have a Wii and a 360, and unless the Wii has a much better control interface, for example Rabbids, then we buy the 360 version because the graphics will likely be better and we have an HDTV.
Is this a serious issue for Nintendo? It doesn't appear to be right now... they're tearing up the pavement in console sales. I can't honestly say how it will affect future sales, it's just a barrier to porting a number of titles to the Wii. Perhaps the Wii demographic doesn't require those games (because we own both a 360 and a Wii there isn't any angst for us regarding not having FPS games on the Wii, for example).
This post isn't meant as a slam to the Wii or Nintendo... I really like my Wii. I just don't see wide-spread, quality 3rd party support dramatically increasing on the Wii due to the situation I described above, specifically where multi-platform leaning publishers are concerned.
