Single player is alright. I'd say BO2 was the best in this regard.
Multiplayer is fairly fun but repetitive. I usually get each game, play it for about 15-20 hours over the course of a week, and then never touch it again. Ghosts is actually the first game in the series I haven't bought around launch since MW2. I've watched people playing it on YT over the past few days and it just looks like a worse version of MW3, which is by far my least favorite game in the series. At this point I might just stick to the Treyarch games (especially since I greatly enjoy Zombies).
Anyway, the criticism towards the franchise is way overdone and silly in most cases. It's not a super amazing series but it's entertaining, which is why it gets the sales it does.