Board Thread:Questions and Answers/@comment-88.232.173.22-20131205164650/@comment-1504072-20131205170647

Legacy Collection contains all the HD Editions, so any differences will be a result of those re-releases:
 * the X button now maps to the ENTER command like in Metal Gear Solid 4, as opposed to the O button in the previous games of the series;
 * No minigames such as the skateboarding from Metal Gear Solid 2: Substance, Guy Savage (Naked Snake's vampire-themed nightmare), nor Snake vs. Monkey in Metal Gear Solid 3,
 * No VOCALOID service for ZEKE.

There may be other minor changes (not including cosmetic changes), but don't remember them right now.