As part of the previously released HD Collection on the Xbox 360, METAL GEAR SOLID 2 HD Edition and METAL GEAR SOLID 3 HD Edition are both now available on the Xbox market place for $19.99 coming in at 7.35 GB.
Source: http://marketplace.xbox.com/en-US/Product/MGS-2-AND-3/66acd000-77fe-1000-9115-d8024b4e0840#