Unfortunately, things didn't quite get off on the right foot at the show, though, with the chosen gameplay demo actually showing very little of the game - especially if you're new to Halo - or even if you've only played the games. If you came to see a nicely rendered alien forest, though, the chances are you'll have been left thoroughly satisfied.
Halo 4 picks up where (SPOILER ALERT) Halo 3 left off, with the Master Chief stranded in a faraway place after an accident with a slipspace portal leaves him and half of the Forward Unto Dawn (a UNSC frigate) the wrong side of the universe. Stranded lightyears away from Earth, our hero the Chief puts himself into stasis, instructing his faithful AI companion Cortana to "wake me when you need me". "When", seemingly, is now, as the alien baddies the Covenant have found Master Chief's ship - which means it's time for Chief to get out of there.(/SPOILERS).
The E3 demo picks up a few hours into the game, where Master Chief, having escaped from the Forward Unto Dawn, has made it onto the surface of an alien planet. The picturesque scene is then rudely interrupted as the UNSC Infinity (a ship that plays a large role in both the singleplayer and multiplayer aspects of Halo 4) crashes through the atmosphere above him, closely followed by a mysterious, glowing orange orb that appears and shoots after the ship. It's later explained that this, and a lot of the enemies the Master Chief comes across are sentient AIs, built by the Forerunners (the ancient race who constructed the Halo rings) to defend the planet, and whatever secrets it may hold...
And with that being pretty much the only major plot point you can figure out from the trailer without knowing Halo's lore inside and out - far beyond the level it's ever been explained in the games - it's still enough to get us excited about Halo 4. When it's at its best (as it was in the first game - a level it's never reached since), Halo has always been about being on an alien planet, exploring it, discovering its weird architecture, lifeforms, and enemies, and figuring out its secrets. The story may have become more convoluted, but by taking the series back to its roots in this way, we're hopeful that we could be looking at the best Halo game since the original.
If it has a decent (and easy to understand) story in place, Halo 4 could be the best first person shooter of the year. Could be. We'll be keeping our eyes on this one.