Sony used to always reveal games before E3 but they are most likely revealing everything at this e3 for the biggest effect. Ms still has to show games they announced at last e3.
They are probably going to show Call of Duty, some EA games, Sunset Overdrive, Titanfall DLC Quantum Break, Gears 4, Witcher 3 Forza Horizon, Halo 1,2,3,4,5. They will obviously include a couple more AAA exclusives and an old ip revival. How is that supposed to win them E3? It's moslty more of the same. What Ms always thinks is not what the fans think. To microsoft that list above is megaton. And if they show off the most third party games then they should not win, because those games will be available on ps4. Same goes for sony, they will probably show a few more exclusives and show third parties from ubisoft, Rockstar, Batman Devs, the 2k sprots devs, Bethesda, capcom, konami, Activision( bungie and crash! Believe!). Unless ms money hats multiple BIG established exclusives, they aren't winning e3, only xbox fans will think that.