Halo is awesome and epic and all that, but what I really miss is that the story should have more depth, more darkness over it, like the walk form CoD 3 to World at War.
It should be more close to the desperate struggle of the marines against the Covenant war machine. Like the lone, dark, rainy days when morale is at the bottom, they draw nearer and you wonder if you will survive... A bit like Neill Blomkamp's (think that's his name) films.
The weapons should also be made more credible. Instead of just the glowing Spiker shots, make them like real, enormous, vicious spikes that don't fade away but stay on walls and things like that. That's just one example.
Do these things, add a little more blood, more emphasis on the story and a change of graphics and Reach could be more than the great next Halo game. It could be better than Combat Evolved.
[Edited on 11.03.2009 11:06 AM PST]