It's good to see some viable alternatives to COD this year, I think BF4 will do well more so on next gen where you will get nearer a proper BF experience, I will probably give it a try on next gen but in my eyes there are some fundamental problems with the game. Destiny might do well but I have my doubts, I will certainly wait till its out and see what people make of it and how it plays. Titanfall I think has the biggest chance out of the three to challenge Ghosts for two reasons like iivrruummii said it comes out around the time when COD starts to become stale and secondly its seems to be the evolution of a fast action packed arcade shooter which COD is so it is most like it and I think the success depends whether they get the pick up and play right and balance, I certainly can't wait to get my hands on it, its one of the main reason for the xbox1 purchase.
Another game which I think has probably the best chance giving COD a run for its money is Homefront 2 because its an arcade type modern military combat game just like COD but the sequel is being developed by Crytek this time who have a magnificent engine which features low latency controls and 60 FPS on currant gen and also looks amazing and has been in development for years already and coming out in early 2015. When playing crisis betas I have always wondered what crytek could do with a modern military combat setting and its good to see they are giving it a go.
I would like to play titan fall and if you guys have not had the chance GTA 5 has a pretty sweet teamdeath match