in reach I cared about all of the main characters, and seeing them die, especially in order to allow me to save the human race or whatever, killed me
(hence why I am always, 100% of the time, mad about the way kat died)
on the other hand, the only person I ever cared about in the main series was the arbiter, and I'm pretty sure that's because of weird furry reasons rather than anything to do with the actual story