Is the Wii a success?

[Reasonable]

HW sales - yes (still the market leader and although it's going to bow out first it's sold more than enough units)
SW sales - yes (huge software sales and a lot of it 1st party)
Marketshare vs predecessor - yes (if the 360 is a big jump over the Xbox then the Wii easily outdoes that)
Profitability - yes (HW/SW raked in huge sums)
Market Impact - yes (not just how it altered a lot of expectations for games but drove both MS and Sony to join in)
3rd Party Success - mixed
All genre appeal - decent (didn't have the necessary infrastructure to compete in the online / social genres)

All in all yes.