Legendary is all in with Rodan, Motha and King Ghidorah along with Godzilla. WB will have a field day with the marketing campaign with this one. WB fumbled with K:SI initially but bounced back brilliantly with a late marketing blitz to open 50% above industry projections.
Godzilla will be a much easier sell than Kong IMO and then we have more huge monsters that can catch the attention of the GA. The production for this one will be f**king huge and if it is reflected in the trailers, it'll bring the audience on OW.
What will make or break the movie will be it's legs at the BO. KOTM needs to be a more fast paced Monster romp and Mike D has indicated that he's going to show us a lot more of the Monsters. Godzilla was ultimately boring for the GA and that reflected in it's poor multiplier in the heart of the Summer. The release date didn't help Godzilla but Kong was also in a really precarious situation in a stacked March but came out unscathed with a very good result in the end. KOTM must find a good balance between human interactions and monster actions and if it does that efficiently, good BO results will follow suit.