Halo technically isn't an FPS, it's a third-person shooter
Also, Ubisoft didn't invent Far Cry, they bought the franchise (and royally screwed up 2, though 3 is apparently super good)
At least Halo was original. Players kept clamoring for co-op play for years to deaf ears from the likes of Ubisoft, then suddenly Halo comes in, listens to the fans, and actually innovates, then Ubisoft copies them. They have a few of their own IPs but they're basically The Borg, they assimilate, the incrementally upgrade, but it's taken them ten years to get a decent FPS. They used to play Far Cry 1 at lunch break, FC 2 was shite and everybody knew it. The problem was the producers and executives, they have this holier than thou infallible mentality that only does the right thing eventually, begrudgingly -- and only after exhausting all other possibilities.
I personally hate third person shooters the way they stand now, they're all scripted and silly controls, very disassociated from the action, and slow. Compared to Prince of Persia 1, all the rest were very weak in comparison to what a single russian programmer made all on his own. (if I remember correctly).