sorry heybtbm but thats complete BS... not all (or even half) of the loose ds/gba games on ebay are bootleg. in fact most bootlegs are complete.

the best way to tell is by angling the label of hte cart towards the light so you can see a number "punched" into the label. all official games have it, none of the bootlegs do. its usually a 2 digit number.