Depends on whether you think Wii Sports is the best game ever. I don't - so essentially from my point of view its already been beaten (in fact before it even came out as their are older games I would rate above Wii Sports).
However it is damn good fun - even if I can't seem to get the hang of the boxing. I can comfortably beat my kids, in a heartwarming 'competitive dad' sort of way, at everything but the damn boxing.
Try to be reasonable... its easier than you think...