I think you came close with your point of standards. I don't think it because of games like mirrors edge and dead space not setting the world on fire. It has more to do with them not keeping the same standard when these type of games get a sequel. This on top of their very aggressive business model that does not bring good will, on top of gamers having a chance to be angry that the next game in the series feels streamlined or rushed.
Mass effect, dead space and dragon age are all great games and have made good sequels but you can see the business model effecting these games and making them subpar in some aspect. Mass effect 2 great game but less rpg in nature, Mass effect 3 with good but added-on multiplayer and having a rushed and unsatisfying ending, Dead space 2 unneeded multiplayer, dead space 3 micro transaction with an unsatisfying ending, and dragon age 2 with its reused environments and streamlined inventory system.
All these games feel like that are run into a EA business model standard and have made the game less deep in one way or the other. At the end you have to build some sort of good will by making a new IP and creating something that is fan service. EA seems to have given up on that as well.