The point that is overlooked is that game retailers will often go out of their way to push a used copy of a game over a new one, as it makes more money for them.
Of those 1 million used copies, let's say 20% of those were sold to people who went to counter, box in hand for a new copy of the game and persuaded to save a few quid by buying a used copy that the store happened to have.
Those 200,000 copies are lost sales - the 80% that were only ever going to buy the game used were never going to buy a new copy. Same for people who pirate a game, they too were never going to buy it so technically not a loss (and, in fact, piracy can generate some sales when people try the pirated version and actually decide they like it enough to buy it - might not happen often but it does happen).
It's also not comparable to other industries, at least not in the UK - here second hand books, CDs and DVDs have generally never been sold alongside new ones - I think there have been a few places in the past but very small scale, indie retailers, certainly not stores with the market shares of places like Game and Gamestation.
Here the selling of a used product, alongside, and often in prefer to, new products has been pretty much unique to videogames. For CDs, DVDs and books you generally have one retailer only selling new and another who specialises in second hand.