What’s your favorite Halo game, my personal favorite is Halo Reach.
Halo 2 I had the most “fun” messing around in SP and MP…
Halo 4 was the peak of my skill in MP, so I’ll go with Halo 4. My friends and I just wrecked people.
I had a 1.8 K/D and a 75% win percentage. Losing was a rare occasion 
Halo 2 by far it did not hold your hand or had fancy abilitys just you and your gun
Halo 2 introduced more open levels allowing you to glitch out and explore for the heck of it and it brought skulls for wacky times in campaign. It even had split screen and the story was epic. And you get to play as Elites in an epic multiplayer experience.
Halo 2. Purely because of nostalgia.