Halo 3.
Bonus: More open, more focus on scope and sandbox gameplay. Hopefully not as an excuse to hamfist a battle royale mode into the game. As Shadow mentioned, much of what's killed the spirit of Halo was chasing esport trends with twitchy arena gameplay. Chasing battle royale would be just as bad a mistake.
I don't care as much about balancing if they can increase the overall scope of the gameplay. Halo has always felt like it could naturally fit a huge multiplayer mode with gigantic maps and vehicles to traverse them. Pelicans and Phantoms have been in every game but never truly usable. Elephants were roughly implemented and never really viable. Even something like the Shadow which only appeared in the campaign of Halo 2 used as a carrier for Ghosts. They already have a ton of assets available to naturally implement into a huge multiplayer mode. Just add a squad system similar to Battlefield to top it off. This has always felt like the natural evolution for Halo in my mind.
