Sorry for my english, I really killed my brain last night haha
Anyway, a FPS from Santa Monica would be... disappointing.
Sony already tried, they can't have a very successful FPS, too many contenders.
Sony can capitalize in a genre when they "invent" it or are the first to do something.
Their 3 biggest brands are Gran Turismo, God of War and Uncharted. The "console sim", the "western hack n slash", the "cinematic action adventure tps", they were among the first to try these thing, they were good, they had luck, and became successful.
No way Sony can "invent" a new 5m+ success with FPS, the market it's full of these things.
1) They need to invent a new subgenre or choose a subgenre without a strong champion
or
2) They had to choose a subgenre with only one "champion", and try to be the 1st rival. The market can hold at least two great contenders.
Western RPG can have another big contender, it has a lot of subgenres. First person, hacknslash, turn based, third person, action and so on. Sony doesn't have one yet.
GTA-esque games are too may, but no one had a true success. They have infamous already planned, but it's a lot different. They had The getaway. I think that a new hyperrealistic title (stunning graphics and animations, high production values, top tier AAA developer, car licenses, true cities and places, multiplayer) could be a win.
Third person action adventure genre is also almost done (open world Assassin's Creed, tps Uncharted, comic Batman, maybe the survival The Last of Us). If they choose this path they have to invent a new subgenre, not already covered or use a unusual existing subgenre. How about a title with a dense and complex plot and mystery that makes people want to know how the story ends? Phenomenons like Lost or Death Note played a lot on it. Every new game would be an "event", people understimates the power of a good plot.