Perhaps he's judging those games by their innovation and the success they've found with a huge, previously untapped audience. Maybe ten years ago he didn't think games like these could be possible, or even successful, and this realization excites him as his work goes forward.
What I find interesting is that he specifically stated Wii Fit Plus and Wii Sports Resort, and not Wii Fit and Wii Sports. I actually wonder if this means he didn't expect that he would be creating sequels that are so direct, and would have had more creative freedom to make something more unique.
Like you say though, his comment can be interpreted in many ways, so it's anyone's guess what he actually meant.