Ive seen people say that Halo 3 story was stupid and Halo 2 > Halo 3.
Ive also seen people say Bungie did a good job in finishing the story.
Now I own Halo:CE and Halo 2 and I do think Halo:CE story crushes Halo 2 because Halo 2 ended in a horrible cliffhanger. But Halo 3 was not a cliffhanger and it was just as epic as the first one. Halo:CE is maybe slightly better but Halo 3 really did a good job in finishing it. It also finishes it in a way that makes a new Halo game possible. Even though they said it's the end, I know MS is not gonna let that happen.
Obviously they're won't be a Halo "4" but there will be another Halo besides Halo Wars.