I actually liked older CoDs a lot and I would really really like to love newer ones as well. Pretty much what I can't understand about CoD is that the things I loved about CoD 4 are ruined and it seems that they don't have interest to fix things that actually need to be fixed.
Gun balance: probably the most horrifying thing about never games. You unlock new weapon! That is nice, but unfortunately it actually is just bad and it is better to use these OP FMG-9 alien beetle weapons that kill people in seconds and are as accurate as in other guns in game. Use these, or be killed by these!
Map design: seriously, I played MW3 like ten hours and I didn't find one memorable or actually fun map that I wanted to play in.
Not putting focus on interesting game modes: seriously, HQ pro was my favorite game mode. I haven't seen anything similar in other games and it actually forces on some kind of team co-operating. but no, give us TDM and some Kill Confirmed and everyone is happy running around map killing everyone who comes across you.
No interest in actual competitive gaming: the game does not have different matchmaking for ranked gaming where you could actually do something competitive, so have fun and play forever with scrubs.
Seriously, I like gameplay and campaign is some nice fast paced action that you actually want to play to the end unlike campaign of BF3 which is horrible. CoD franchise could redeem itself by giving some time to itself and trying to refresh old formula and making something revolutionary for next gen like they did for current gen with CoD 4
And yes, DLC practice of Activision is horrible.