OMG JXZAW, the very reason the world knows Halo is cause of Halo 1-3, combat evolved is the first FPS to capture the immagination of all who know and respect gaming. When you compare FPS and see games like Nova and Destiny etc, the very first thing that pops into your mind is Halo.
The reason why you can't understand the difference in the story line is because your a game leach, you just play whatevers out there without rhyme or reason, thats the problem with society we love to take it all and leave nothing, our depth of thought is becoming shalow because whe're to spread out.
But to be fair I was taken towards the end of Halo 4 when Cortana used the remainder of her coding to save Master Cheif, once again reminants of the build between the two in Halo 1 & 3, I guess you would like it.
Halo Reach, yet another example of humanities fragile nature and its ability to be wiped out at anytime, is it so hard 343 industries to catch that, why must you persist with the cosiness of keeping everyone alive?