Gaming account CharlieIntel said on October 16 that Call of Duty: Modern Warfare 4 was Steam's No. 1 preordered game ahead of campaign early access. The post did not explain the ranking method or provide historical sales data, so the position remains an attributed, time-specific claim.
Activision's campaign early-access announcement said digital preorders and pre-purchases received campaign access beginning October 16, including purchases on Steam. The Steam store page showed advance access as active ahead of the full release.
Steam describes its live global Top Sellers chart as a revenue ranking. A later saved snapshot placed Modern Warfare 4 at No. 4 overall. Because that chart is dynamic and covers all sellers rather than only preorders, the later position neither confirms nor disproves the earlier preorder-only claim.