Wii sports is this generation's version of the NES version of SMB.
SMB was a bundled game that was enough for nintendo to "get its foot in the door." And was probably the only game a lot of people owned.
Likewise, i think Wii sports is doing this in the same way, getting its foot in the door so that people will buy it up. Since Nintendo already makes a profit on the system, then it wins already. Any extra games the customer buys goes straight to the bank. Of course, if its a 1st party game, then 100% of that money (minus development costs, etc. etc.) goes into the bank.








