Overall Storyline

The Halo Rings only destroy life of a sufficient biomass to support the Flood, so the rings wouldn't have destroyed any old ruins. But notice not only did humans not discover ancient ruins of their own space faring civilizations, they also never uncovered the Forerunner assets on Earth buried beneath Africa that turned out to open a portal to the Ark. It took Covenant (Forerunner-based) ships to excavate that, so its possible traces of humanity could have been covered by sentinels as part of the Forerunner's reclamation plan for the galaxy after the rings were fired.

They did a terrible job of explaining what was going on.

This is likely due to all the info put on Halo Waypoint, the books, etc.

I've played 1, 2, 3, ODST, Reach, and 4, and I had to piece together what they said happened in 4 with two run-throughs.

I just finished my second go-through and I'm still fuzzy on basic details. How did MC survive detonating a nuke **manually**? Supposedly Cortana used the last of her power to save him, but... What? How? No, seriously, HOW? No explanation. She just did. Don't ask.

Halos 1-3, Reach & ODST focused on the Covenant War, and the Forerunner stuff was out there on the horizon. They did a wonderful job of doing that, but never at any point in 4 did I get the overwhelming basics that really would help explain just what the heck was going on.

All I needed was a "Long ago, humanity owned half the galaxy, but ran into a race called the Forerunners. They fought and fought, but one day X happened and humanity had to go evolve all over again while the Forerunners stayed in stagnation, imprisoned on some weird planet."

Instead, what I got was questions:
"So, who are these Forerunners?"
"Why do they want to off and exterminate humanity?"
"Why are the Covenant against them, then helping them?"
"Why are the Covenant even freaking there?"
"How can humanity be so powerful in only four years after Earth was devastated?"
"How did all this start with MC and Cortanas ship **somehow** drifting through the vastness of space?"

Much of this is probably explained here and there, but it wasn't OBVIOUS and EVIDENT to the casual gamer just making his way through the single player campaign. I felt no tension at any point in the game, other than "kill these bad guys to advance to next level". No involvement with the story, nothing.

Storytelling FAIL.

The Forerunners actually traveled to Earth long time ago to bury their structures. Forerunners left all of it to mankind (unknowingly to the humans). The reason the Covenant war started is because humans were considered "Relics" by the Covenant and the Prophets decided to hide this and declare war in order to have the Forerunner artifacts to themselves.

If you're really into science fiction, the Halo novels really are superb...especially the first four: Fall of Reach, The Flood, First Strike, and Ghosts of Onyx.

"Your punishment shall match the magnitude of your failure."