I think this will be the case amongst most Sony fans, due to Sony having lots of announced yet unreleased games. Not many of their studios are working on projects we don't know about now, so there isn't many possible exciting new announcements. Meanwhile, there'll be at least a few announced games that people really want to hear more about. I'm really excited to hear more/ see more on Spiderman, God of War, GT Sport, TLOU2, Detroit and Uncharted.
For others, they have a bit more potential to announce games and not many announced so the excitement is different.
As for third parties, the trend has definitely become to announce with a trailer before e3 before showing gameplay and more details at their show/shows. Because of this, there isn't going to be many big, exciting third party announcements. Its all going to be about gameplay. COD WW2, Battlefront 2, Destiny 2, Far Cry 5, Assassin's Creed, Red Dead etc. have already been announced