Well, maybe instead of shifting their focus to PS3/360, they should shift their focus away from mountains of shovelware on Wii/DS to giving quality support to both HD systems as well as Nintendo's systems? What's that, Ubisoft?
Too much like hard work?
Yeah... Thought so. Too many third parties view Wii market as being a place to exchange quick, cheap titles (mostly rubbish) for quick, easy cash. I'm glad it isn't working. I only hope that the quality Wii games coming out this year like NMH2 and Monster Hunter Tri get a good reception and make third parties realise that if time and effort goes into a Wii game, they'll get good results.
Failing that, as others have said, I think Nintendo need to expand and invest more in their first and second party portfolio. 2009 showed that too few third parties will pick up the slack when Nintendo step aside, and that every third party will complain when they have to compete with Nintendo's titles. It'll take time and money, but I think Nintendo need to expand how many quality titles and genres they can push out each year. Clearly third parties are not interested, and Nintendo should expand to take as big a piece of the pie as they can.