The most important part of any game, even more important than the
gameplay itself
At least, according to
today's youth, who tend to forget decade-old games that had pioneered the ideas made popular by these new games.
See also:
crysis
Crysis is
touted as having "the first real time Predator like gameplay" when in fact there was (gasp) an Alien vs. Predator PC game tied into
the franchise, released in 1999 -- Crysis just has better graphics.