You're onto something there, even if you were just trying to be glib. If you pay attention to the marketing copy of CoD games, they only talk within the scope of the franchise. They don't care if other games have done X feature or used Y tech, they care if a CoD game has. CoD has a distinct player base in games, namely, they have a lot of players who don't otherwise play games. They have the metrics on this and know that their primary competitor is themselves. They need each release to be different enough from previous ones to justify a purchase, but not so different that it doesn't appeal to their unique column of players, the ones who only play their game.
This is part of why other companies, especially EA, are so silly in trying to make a CoD Killer. How do you convince people who typically don't play Other Games, to play Your Other Game which doesn't look that different from what they've already got, but it is on untested grounds? As one YouTuber put it, the CoD Killer is the game that is nothing like it but appeals to CoD players. Minecraft thus far is the only thing which has posed a threat.
Now as for "unique weapons", that depends on the goal you have in implementing weapons. I wrote this almost two years ago, but it still applies:
http://scar3crow.com/2013/04/am-gun-will-travel/
Now, I wouldn't call myself "excited" for Black Ops 3. But I will keep an eye on it, because Black Ops 2 was by far the strongest entry in the franchise, and this is the first time that development team has had a three year cycle to work with. It will still be Call of Duty, with all the faults that implies, but I've always found it interesting to observe how these teams balance the demands for change and the requirement of familiarity.
I will say though, if you play Black Ops 2's multiplayer for a few hours, and you don't feel the difference between the weapons - to the extent that you develop particular favorites, and find your play style adjusting to them - then I would argue that CoD is actually too involved for you. It isn't a good game, but it is, when on point, a game about focused differences and applying them correctly.