The reason Wii had a bad showing this year is they were catering to an audience that wasn't there. You can't try to sell your console to a casual market and expect those casual gamers to follow a big tradeshow that generally caters to hardcore gamers.
I think they were talking to an audience that simply wasn't paying attention / wasn't there.
They were catering to the nongaming press which was there. Nintendo knows gamers will pay close attention to all the news no matter even if they don't show all the games at their press conference (they released a lot more information about games actually after the press confrence). But they knew to get the nongaming press's attention they actually had to show it at the press conference and let gamers pick over all the text/video information they release afterwards. At the moment a lot people seem to be ignoring Nintendo is releasing more actual games (in addition to more nongames) for the Wii than they ever did on the Gamecube.
As a result their press conference succeeded for the people who the conference is actually meant for (which is not the gamers no matter how much we hate it). I mean why bother showing us information we would find other ways no matter how hard they make it for us to find?