Not quite as every one of those games you mentioned has a completely different single player storyline for a start. Sure the multiplayer is "similar" but black ops has 100% new maps with no rereleased ones from MW1 (which MW2 had in the DLC packs for example). Theres vastly different weapon balancing in each game, not to mention their approach to killstreak rewards, levels of prestige and how you unlock new equipment (which bfbc2 didn't do very well at all).
To say no effort is put into these games is abit silly really, considering the budgets for the newer ones have been extremely high and they are also some of the best cross platform games going, with the PC version STILL feeling like a PC game...
They pretty much have to do a Singleplayer. Doesn't matter how bodged together it is. Once thats done they just have to take it and create a bunch of maps off it. Certainly not worth the £40 asking price for that alone and the MP is just the same with a bunch of minor alterations
The rest of it... you actually call altering how Prestige works a time consuming event that took effort? Unlocking? You seriously telling me they did it better than BC2? 1 of the best guns in the game is restricted to level 44 or something, most of the rest are arbitrarily held back until you've got enough cash and the Pro perks are held back until you've completed arbitrary 'challenges' AND got enough cash. Balancing/handling of the weapons is the only part that might take a while, but considering 75% of players appear to have mouse 1 bound to prone+fire and mouse 2 bound to ADS+fire, I think they did a pretty **** job.