For me, I think halo 3 had the best campaign, halo 1 is the most fun(nostalgically), but my all time favorite I think was halo reach. I think the story was great, firefight great, forge was incredible. It made custom games so alive and active. I think it had the best multiplayer, especially the introduction of infection in a online playlist.

Just got destiny 2, and makes me wish bungie was still making the halos.

( I had to make new topic because I forgot reach)

Halo 2 is the only answer.