Since Warhawk is coming out first, some may pass it by since they plan to purchase the latter two anyway and can't stomach the investment for two or all three. Some might pass on Lair because they're still playing Warhawk, but will pick up Heavenly Sword since it comes out a bit later. Even still, Heavenly Sword may get ignored because it comes out last in the trilogy of releases. Some people might not want to buy it, as they're still enjoying the other two. This is all assuming more than one of these games interests you, but if not, just think abstractly about which of these titles is most likely to get overshadowed.