I understand "X is in the game", but without a definite subject this phrase becomes meaningless to me. It's been used by EA Sports and other companies to advertise they have something special about their games but this lack of specification of what's special about it troubles me.
Literally, to be in the game in such contexts means to be playing a [competitive] game, with the implication that you're a contender for winning (compare you've got to be in it to win it).
Advertising slogans don't necessarily need to follow standard idiomatic usages, and we don't have any specific examples to consider anyway. But in normal speech the only variation you're ever likely to encounter is something along the lines of...
Manchester United were 2-1 down at half-time, but they've switched to a more attacking play now, and they're definitely still in the game.
...where it simply implies United still have a chance of winning.
The original version of the slogan was "If it's in the game, it's in the game", meaning that EA's sports-based video games captured everything interesting about the sports they represented.
Eventually the slogan became so familiar to gamers interested in games of this sort that EA truncated it to just the consequence clause.
muru asks for a source.
Here's the website of Jeff Odiorne, who with with Michael Wilde developed the original campaign at Goldberg Moser O'Neill and Riney. A brief video about it is at the bottom of the page.
Here's a story from Ad Age about Odiorne and Wilde's work after they left Goldberg and started Odiorne Wilde Narraway Groome with EA as their principal client. It includes this:
Goldberg won the account in August, just in time for Odiorne and Wilde to create a campaign to launch the EA Sports line for the Christmas season. The two came up with the position of authenticity that was based on not only a knowledge of sports but a passion as well. Their tag, "If it's in the game, it's in the game," was deceptively obvious, [Doug ]Transeth [VP-sports marketing at EA] adds. "It was so simple," he says, "it scared us." [my emphasis]
And here's a record of the trademark history, drawn from the US Patent and Trademark Office.
And just for lagniappe, to demonstrate what Odiorne and Wilde were after, here's an example of a fan praising the attention to detail in a recent edition of Madden.
The idea is that whatever you might ask for or expect, It's In The Game.
There is a general idiom, in advertising, of a slogan answering a question the audience might be expected to ask. From that, we get some slogans that answer multiple possible questions, cf. Prego, "It's in there!"
Some of these start out in a longer form, like "If it's in the game, it's in the game" or "Homemade Taste: It's in there" but over time change to the pithier version.