The idea to make multiplayer free to all was a stroke of genius. It'll likely bring in new players and those who fell off the wagon with games like 5. Personally I will take what comes with a grain of salt, the storyline looks promising, new Cortana and all that, but will it have that spark the originals had? We'll have to wait.
Personally, I really enjoyed Halo 5's multiplayer. I thought it felt satisfying and consistent to play. Unfortunately, I cannot say the same for the campaign since you hardly play as Cheif. Hopefully Halo infinite will bring the series back into the mainstream.