Sorry catching up with the thread and just saw this.
When I arranged my favorites in order, my preference between each game is kind of minimal. IMO Halo 3 is still the best since it offered the best variety in locations, offered the largest vehicle battles, and had an awesome scope throughout the entire campaign. The brutes as the main enemy is probably my biggest let down with that game since even after Bungie's changes, they were too easy to pick apart from afar.
Halo CE will always have a high place in my list because even though some mechanics are a bit lacking or dated, the overall experience still holds up very well after all these years.
I've enjoyed Halo 4's campaign very much, even with the random issues and lacking banshee segments. Otherwise I thought the scope was pretty much kept intact for the on foot & vehicle sections and the gameplay is as tight as ever.
Halo Reach is still great even though I've played some levels, like Swordbase, too many times because of those challenges. =p However the art and music in every other Halo was more appealing to me and while the on foot battles are on average larger than those in halo 3, I thought the vehicle sections were lacking in scope. Also just like how Halo 4 relies too much on duplicate objectives for padding, I thought Reach relied too much on those firefight skirmishes in the campaign.
Finally onto ODST, I very much enjoyed the HUB world (even though it was basically the same half world copied and reversed), the self-contained story, and the levels in the game itself. They offered a nice variety that played to the key characteristic of each squad member. I also enjoyed the extra vulnerability from being an ODST instead of a spartan and the improvements they made to the brutes. However I didn't care for the silenced pistol or SMG, especially since the "silenced" part never played a part in the gameplay. Also even though I enjoyed what was there, the campaign still lacked in content compared to the other full-fledged Halo titles. Last, while I enjoyed the story, it was rather inconsequential in the overall universe.
As for Halo 2......well what can I say? Great job at expanding the universe, awesome story (until it ends) but the game lacked in scope for the sake of graphics and looking back, you can definitely tell the campaign lacks the polish of every other Halo in the series. I also didn't care for the Arbiter levels, but I don't know if that was due to the character I played as or just the uninspiring level design. It's easily my least favorite Halo game and the only game I've completed once on legendary never to play through again.
Well I'm not sure how I got on this long explanation
, but hopefully that helps answer your question. :smile: