I'm still sad that the BEST Halo twist didn't make it past CE. At Two Betrayals, Guilty Spark says
> "Last time, you asked me, if it were my choice, would I do it? Having had considerable time to ponder your query, my answer has not changed."
>Last time, you asked me
This just confirms that Chief was alive and active when the Halo Ring was fired before. Given it sterilizes all sentient life that long ago, it would've taken several thousands or millions of years for life on the way to evolving into humanity into becoming humanity. And humans can't live for thousands of years but Guilty Spark's advance sensors shouldn't be wrong, and he had no dialogue whatsoever saying Chief should've long died of old age. What this indirectly revealed was that Chief is an ancient space alien who can live for over a million years or at least the length of time it'd take for a non-sentient life form to evolve into humanity.

It could've been so interesting a plot into Halo 2, on how Chief was found by the UNSC, or why he lacks memories, or any plotline that could've resulted from the knowledge that our protagonist has lived over a hundred times any human being can. Then Halo 2 had to pretend this line never happened and so did the rest of the franchise.