^ True. But those characters were very much supporting characters and I don't believe (but an subject to correction) that solo films are planned for any of them beyond general 'maybe' replies to interviews. The logo for the Superman/Batman one contains both of their symbols so it really looks to me (at this admittedy very early stage) like a joint movie, as oppose to the Marvel approach of supporting roles from other characters from that universe.
True, this. Sure sounds like a joint adventure, which isn't going to appeal to everyone who isn't an enthusiastic fan of different comic series. More casual comic fans or non comic fans who might happen to enjoy an individual movie series with Superman, Batman, Ironman et al will look at a title like Superman vs. Batman and ask, "What?"