Mostly talking about IW games. It felt good to actually be able to kill something with one burst, provided you don't aim like a noob. I don't know how anyone could like the M8A1. It's almost always a 2 burst or more to kill. Doesn't feel very fun to use.
I personally don't think any guns from 3arc games have very been fun since WaW, but that's a conversation for some other time.