Infinity Ward is no doubt resting on past successes. COD4 completely changed online multiplayer and Infinity Ward's COD games (Modern Warfare series and now Ghosts) has been almost unchanged while Treyarch has taken the COD4 formula and has been leaps and bounds more proficient in adding on with its Black Ops series.
VERY short campaign, ridiculous levels in space that'll have Neil Degrasse Tyson on a rant for weeks, and a story that could have been considerably more fleshed out. The story is admittedly better than MW2 and MW3, but those two were absolutely terrible.
If you were only interested in multiplayer that's fine. There is really nothing new. They basically copy and pasted Black Ops 2's multiplayer and added a facelift. In fact, there are noticeable deletions like the mode I play: Ground War. No ground war. Only 12 players.
Save your money. Just play Black Ops 2.