Well I've put in some time on Ghosts, and I seem to be the only person in the world that likes Infinity Ward better than Treyarch. I hated Zombies, the wildly popular minigame, since I found it difficult and repetitive. I have enjoyed the Extinction aliens game better so far, although i admit I haven't gotten very far.
The campaign is vastly superior to the last 2 releases in my opinion. I didn't finish the campaign in the last two years because I had no clue what was going on, and the cut scenes were endless and incomprehensible. Who the hell was attacking who? Who was brainwashed? Or double brain-washed? I didn't even know what decade I was in half the time.
The story this year is a linear, simple plot in the near future. South America attacks the U.S. Done and done. Add in classic elements like brother and their father, and a rogue super agent, and it's great. I enjoyed this story a lot - the gameplay, the story, the ending, everything. Lots of vehicles, good missions, etc.
Multiplayer is good but I have a couple of objections. You seem to die faster than other CODs, and it was fast already. Now it's instant. Also, at first I though people were whiners, but I have to admit the maps are laid out kind of funny. In Domination, the center area is often way closer to one group, or not anywhere near the center of the map. The castle map is way too big - it takes a minute or more to run across. They also removed a couple of the objective based games, like Demolition, so there's a ton of just running around randomly for games like Cranked or Kill Confirmed. I do like how you can rank up your multiplayer squad playing against 'bots - really nice for casual players.
Overall, I think it's a B or a B+, with multiplayer needing the only tweaking.