The SPAS in MW2 can be as useful as a primary on certain areas of maps, sometimes a majority of a map. However, I don't think it really is that overpowering as a secondary. It's not like people are shooting both their primaries and secondaries at the same time. Most people are just going to stick with one of their weapons their whole spawn unless they run out of ammo. You could argue its overpowered because someone can have an assault rifle and shotgun and dominate all ranges: long, mid, and short. However, the shotgun isn't the end all awesome weapon for close quarters. It has its disadvantages and advantages. When you know an opponent is around a corner or wall, you can't prime your shot and pre-fire when you go around like you can with automatic weapons. Furthermore, in a firefight with a shotgun, missing is very unforgiving. You usually get only one shot to either hit and kill the person, or to miss and die by his/her 3-8 shots at you with their AR or SMG. I'll give you that the spread of the buckshot does make it hard to miss your shot, but it still can happen if you aren't careful and don't know where to look when you enter an enclosed room. Furthermore, if you run into two or more people with the shotgun, it's significantly harder to kill both of them and live with a shotgun than with an AR or SMG because you can't just spray across them. There are also those cases where you have have you reload your primary in the middle of a firefight and swapping to a pistol to finish them off is much faster and will probably save you.
The shotguns in MW2 were insane, to the point where I'd just use them as primary weapons, I remembered running around with the Striker extended mags (18 shots) because it had the longest range of any of the shotguns. I was killing people in 2-3 shots at ranges of like ~30 yards, it was hilariously broken.
Disregarding the Masterkey attachment, the SPAS actually has the longer effective range.
Anyway, my personal unpopular opinion about MW2: I enjoyed it much more than Black Ops. The OMA Noob Tubes, Heart Beat Sensors, Stopping Power, Commando, Thermal Scopes, quick scopes, overpowered killstreaks, whatever people bitched about; those things made the game more exciting and interesting, whether I'm using it or it's being used against me. It's like they dumbed the game down to something much simpler in Black Ops. I can understand that, making it more centered on shooting skill, but that can get repetitive fast when there are few other 'viable' options. Also, the MW2 maps are much better.
That said, I do hope that MW3 has more of the flare of MW2 rather than the bare bones of Black Ops.
