Separate peripheral for each game.... So for multiplayer PS2Tennis you would need a $129 ($99 for christmas?) a $30 Tennis Game w/one controller, and figure they might sell extras for $20 (unlikely). Never mind the other games.
Even if you already own a PS2, it's still $50-60 to play one piece of Wii Sports.
Any kid/teenager/grandmother who gets this instead of the Wii for xmas will be very mad.
I would cite regulation, but I know you will simply ignore it.