Not only am I against objectifying women, but I resent companies thinking they can just sell me shit by flaunting some babes.
I don't think any company at E3 thinks that. What they likely think is that they can attract more attention by flaunting some babes. Hopefully that attention will cause them to sell shit, so indirectly, you are correct.
Of course, the reason they think that is because it tends to work. If I have a choice between some nerd saying "come try this game" and a hot 'babe' saying "come try this game", I'm very likely to go try the game the hot 'babe' is pushing. If that makes me "manipulated", so be it.