" @Killjoi: It's not my call, but I'd say the thing that qualifies "game" pages to be "game" pages is being an actual game. Requiring another game to play it disqualifies it from being a "game." But again, I don't make the calls, it's up to one of the staff. "That's an odd stance to take when there are "games" like Cataclysm that require not one, not two but three prior games to play (Original WoW, Burning Crusade and Wrath of the Lich King). Trying to fit all that information on a single page would be quite the task.
Even Wikipedia, a database infamous for its stringent rules against superfluous pages, lists Undead Nightmare, Awakening and Shivering Isles separately. Why exactly are you so zealous about deleting these pages on GB, when they clearly serve a purpose ?