It seems foolish at this point for any game to not be sold in download form (though I think hard copies still make sense as well). Downloads have an inherent advantage: they're more conducive to impulse purchases.
Get gamers used to buying games online and you're all but guaranteed to sell games via impulsive decisions. In less than two minutes, a person can buy a game on a site like Direct2Drive. It's so much easier to coax a person into buying something momentarily than to get them to plan a later purchase.
The game industry desperately needs something like iTunes, one place where every product from every company can be downloaded. In fact, I no reason to settle for something like iTunes... start signing deals with Apple, and Amazon. Do that, and sales will increase exponentially.