Battlefield 4 review ignores the faults of the singleplayer campaign and gives the game a good score because it focuses on the strengths of its good multiplayer. Killzone Shadow Fall review focuses on the faults of the singleplayer campaign and ignores the strengths of its good multiplayer. and gives it a lesser score.
Based on general public opinion and review reception, many people would argue that Battlefield 4's campaign is shoehorned in and barely qualifies as a worthwhile singleplayer experience, whereas Killzone's SP campaign had many strengths and interesting sections (even though it is flawed, it isn't nearly as throw-away as BF 4's SP). But let's take an objective look at this instead: most people can't even seem to play BF4. Check their forums and it's an endless bout of people yelling at DICE to fix the game (on just about every platform). Conquest on PS4 is completely broken and according to many people it has been broken since beta and DICE never bothered to fix it. The minority are the people not experiencing problems.
Furthermore, BF4's multiplayer is severely limited on the PS3/360 versions compared to PC/Next-gen yet that seems to have no impact on their platform's review scores.
I'm not even a reviewer and all this stuff is plainly obvious to me, so why isn't it plainly obvious to the people that are paid to do it for a living? How can they ignore so many significant problems with one game and focus so much on minor problems for other games? It makes absolutely no sense. The exact stuff that consumers should be warned about is being glossed over...but why?