About 6 months ago I was using Charter and never noticed any lag in my online games. I've moved recently and got AT&T Uverse (18 Mb down, 3 Mb up). When doing speed tests, I get about this pretty consistently with a <30 ms ping to a server pretty close to me.
After not playing much online, I've tried both Black Ops 2 and Halo 4 in the past couple of months. While there isn't overt lag (stuttering, freezing, etc.), it seems like there is minor lag that seems to be throwing off my aiming, especially on Halo 4. It happens in every game...I'll put 6-7 headshots on someone (completely certain) and they won't die. Having a shootout with a friend, he actually said he was only half health after 5 seemingly perfect headshots.
Another thing - when playing Spartan Ops or cooperative single player online, no matter whether I'm hosting the game or I'm in my friend's game, there seems to be input lag (as in, I push A to jump and it jumps a split second later instead of right when I push it). My friends says this doesn't happen to him.
Can anyone explain what is happening here and how to fix it?
It's because online gaming is truly still a thing of the future. In competitive games, a tenth of a second is the difference between your shot hitting, and completely whiffing. After going through the tubes, the protocols, the modems, the routers, you're going to see some lag. They try to hide this latency by using lag compensation, but more often than not, that just screws you up even more.