The fact that they are the most played modes means nothing really. The modifications made to CTF to create Blitz made it easier to trap and repeatedly capture an objective. S&D was only removed from the public playlist, so that's not much of an argument. I consulted for MLG for a number of years, and the driving force behind everything they do is the "Pro" community: many of the changes are consistent with previous moves made by MLG when designing their competitive settings. I wouldn't be surprised to learn that the GB/MLG community loves Blitz to death.
Quick forum search proved me right. I worked for those people for far too long not to recognize their influence on something. They fought for years to get this partnership with Activision with the specific intention of having a voice in mode development: I sat through the Skype calls that ran into the wee hours of the morning.
Well im not a consultant or anything special but just judging by tweets and posts ive seen a lot of people asking for CTF and Hardpoint back say that they want it for competitive stuff. Again, im just judging by sight, but I think that a lot of competitive players are upset with the new game modes.
Also, I find it very interesting that MLG is now partners with Activision. I might get around to making a thread about this later. Seems to me that it could potentially lead to bad things for the average player, especially seeing how much disdain "pro" players have for "pubs" lol.
Headquarters was mine and my 10 friends on XBL most played mode since MW1. We almost exclusively played HQ becasue as you said, it took skill , coordination and communication to win. My fav part was always holding the HQ and with the perks/classes in this game, there are SO MANY good combos I could come up with for holding the room with the HQ in it. I also like that the "noob tube" aka grenade launcher is much weaker in this game so it would definitely make HQ more fun to play.
PLEASE FOR THE LOVE OF COD IW, BRING BACK HQ!!!