Online became boring to play, since it turned into a camp/spam fest.
It's always been that way, from the first game, up to WaW, that's why I've never playing the CoD MP games.
Call of Duty series lost it's edge when they decided to go Halo with the regenerating health system in Call of Duty 2
Scuse me, are you freaking serious? The game is not defined by whether you get random med kit drops from enemies, or whether the health regenerates. CoD has already been a linear shooter that you just ride the rails, doesn't allow for much exploration witht he constant respawning enemies. With that style gameplay, I'll take regenerating health over dying repeatedly trying to find a health pack in the area just so I can progress through a level.
Call of Duty sucks, I don't see what people see in it.
Then why are you debating quality amongst the different games? Other than the leveling/reward system, not much has changed from CoD to CoD5. Call of Duty 1 & 2 certainly do not stand on a pedestal above 4 & 5, whether you like the series or not.
I mean respawning enemies?
You are about 6 years late to that debate. All of your complaints have been in all versions of CoD since the first game...which takes us back to the point about how the hell you can figure CoD has gone downhill from United Offensive, when nothing has actually changed much except the leveling & reward system.