If you guessed Halo Reach you were correct. People may have different views on it but its my favorite. It has a good campaign, and in halo waypoint you can use the G's on XBOX to unlock hidden armor. The best thing is the multiplayer, it has a very good selection of game modes to choose from, including infection. The multiplayer also has achievements. Including ones for crushing a car or just ranking up. There are no sign of noobs in halo either. Probably because of the gravitational pull Black Ops 2 has on them, making halo all the much better.
Back on with multiplayer I'm going to name off a few of the game types there are. They have infection, you start with a shotgun if you are a human, an electric sword (energy sword) if you are infected. Only 3 start infected the rest human, the goal of the game is the infected to infect all humans and to create zombies out of them. Once humans are zombies they infect other humans. Once all humans are gone the round ends and another begins.
I'm not naming all but, I'm naming my top 2. The other is invasion. It is the best of the best and my favorite of the two. It starts out as one team trying to capture one of two points, all you have to do to is stand in a highlighted box for 20 seconds. Once that step is over the same step is repeated in another part of the map. The last step is to take a glowing intel unit to an LZ once that is over the team that was defending becomes offense and the other way around.
Another good part is forge, unlike COD you can actually take a blank map and make an entire Map yourself. From that point you can invite up to 16 people on a map you made. The other mode is called Firefight, it is halo's answer to Combat Training. In all halo is 10 times better than COD. If you agree or disagree post it in the comments