Halo 2 was a rushed job; even Bungie admits it. Many campaign levels were cut, including all of Act III. This is Halo 2’s Campaign as it should have been. Please note that mission names are strictly conjecture.
The Great Journey
Cairo Station: This level contains The Heretic, which is an introductory cutscene, the Armory, which is also an introductory cutscene and a tutorial, and Cairo Station, which stays virtually the same.
Covenant Ship: This was a canceled level that involved John-117 jumping onto the second ship in Regret’s “fleet”, traversing it, neutralizing the crew, and eventually fighting the first boss; a Drinol, which is a huge hairy monster, at the end, before destroying it.
Scarab: This is the missions Outskirts and Metropolis combined. Otherwise, they are unchanged. The mission is codenamed for the Scarab fought at the end.
Earth City: This is the mission featured in the Halo 2 - E3 2004 Demo… the amazing looking mission that never got into the final game, albeit with a few obvious changes at the beginning and an extension at the end.
Gas Mine: This is my unimaginative name for the levels The Arbiter and Oracle combined. It starts out as The Arbiter, the level Oracle starts half way after the epic Banshee dogfight, and you fight the Heretic Leader at the end. You play as the Arbiter, and the level is the same as the two from the official game.
Delta Halo: Same as it is the same as it is in the official game. Combined with Regret to form a much larger level. The Regret segment starts half way through, and it is exactly the same as the original game. Regret is fought at the end.
Forerunner Tank: This is the name Jason Jones gave this deleted level that takes place in the bowels of Delta Halo, presumably fighting Sentinels until you get to the area under the Library where Gravemind awaits. You play as John-117.
Sacred Icon: This is the collective term for the levels Sacred Icon and Quarantine Zone. It is unnecessary for this level to be split in two, unless the Library segment was extended, and no one wants that. You play as the Arbiter.
Gravemind: Exactly the same as the one in Halo 2.
Uprising: Same as it is in Halo 2, with maybe a bit explanation as to why you’re there. You play as the Arbiter.
High Charity: Same as it is in Halo 2.
The Great Journey: Exactly the same as it is in Halo 2. You play as the Arbiter and kill Tartarus at the end.
Dreadnought: This level takes place on the Forerunner Dreadnought. You fight Brute Honor Guards and other Covenant until you escape.
Sierra 117: This is the same as the Halo 3 level, without all of the awful Halo 3 features.
Crow’s Nest: This is the same as the Halo 3 level.
Tsavo Highway: This is the same as the Halo 3 level.
The Storm: This is the same as the Halo 3 level.
Floodgate: This is the same as the Halo 3 level, but with awesome the indestructible Halo 2 flood (not those nasty explosive Flood in Halo 3) and no annoying Pure Forms. Boss is a Flood Juggernaut in the crashed Covenant ship segment, which is extended slightly. I’d somehow like to incorporate a Warthog run here
Sorry about the unimaginative level names and combining some levels. I’m not an expert game making company. I honestly think that Halo 2 would have been so much more popular, received better, and altogether far funner if it was made somewhere along these lines. If a Halo 2 remake is made, 343 Industries, please add the extra levels.