Mine will always be Combat Evolved, due to countless hours of playing through the campaign with my friends. Sometimes we'd mess around and do some crazy stuff with the physics. This was long before Xbox Live existed, for those that don't know. Xbox Live launched a year after the original Xbox did. Combat Evolved would not be Xbox Live compatible either. We had some work arounds for this, so we could play people somewhere else, it wasn't always great, but it worked.
I didn't like Halo 2 at first because of the cliff hanger ending, but playing it again, it has a really good story. I wouldn't consider it the perfect Halo due it being rushed and they had to cut most of the story. The game still succeeded and I loved it, for online play mostly. The story is there, but it could have been better.
We finished the fight in Halo 3, and this one is my 2nd favorite, next to CE. Campaign was amazing, and not as brutal as Halo 2. Loved the story, and this was by far the best Halo from Bungie.
Halo ODST was a nice subtle game, loved the story for it because it was different. We were and Orbital Drop Shock Trooper who lands in New Mombosa after Regret's ship jumped into slipspace causing massive destruction. Great side story to show what happened on Earth what we were off exploring a new Halo and stopping it from being activated.
Reach, out of all of these, it has the best and saddest story of all the Halos.
4 was a good attempt to follow up Reach and 343 Industries first game, and the story is good, and it gives you that emotional feel Reach did, it could have been better, but it was their first.
I only enjoyed 5's story because I knew all the lore behind the game, whereas other people probably did not. With that said, I believe it to have the worst story telling of ALL the Halos.
I have high hopes for Infinite, because its trailer made me feel that feeling I felt when I saw Halo 3's trailer. When the pilot wipes away the condensation on the windshield and you see Chief flowing in space and the piano chimes, right there, that moment, I felt it.