I would say for me it is probably bo3, I know people hate it because they got confused or something like that but for me as someone who really likes the storyline I think that was a great ending and a little bit poetic as it is a huge cycle from primis being born then the events of origins happen, then all of the bo3 maps happen, then dr monty sends primis to the great war to give the keepers and humans victory and trap the Apothicons in dark ather so that way primis can destroy them there at the end of revelations and continue the cycle, it all makes sense and is written so perfectly, but that is just me