Click here to see it for yourself. Odd how they have this, but not a pre-ordering area for Sonic Adventure 2?
Yes, the Mario Party-esque "Sonic Square" (or "Sonic Shuffle" as it's also known) is available for Pre-Order at Ugo Direct's Game Dealer.com. It gives a description of it (stats, etc.), as well as a release date of September 15, 2000 (which will almost definately change.