I made a detailed post about why the forge in halo 4 and finding good user made games should be essential. I don’t want to re-write that post, so I’m just going to say look at the success and fun of games like Minecraft and Little Big Planet.
The campaign in Reach was very linear and felt basically like something that introduces you to weapons/vehicles, like it’s just one big tutorial for the multiplayer. I think if you are going to put the effort into making a story (you are allowed to not have a campaign by the way) then you should make it feel like a real story. I’m just going to point out the ending to the Exodus mission (I think that’s the mission) where no matter what you do, everyone dies. Seriously? I can’t play well and save everyone? I know Halo is popular only because of the multiplayer, but the single player could be a strong point if some more effort was put into it.
Speaking of campaign and multiplayer, co-op could be a lot better. If there were more co-op missions that had the thrill of games like Serious Sam then I think a lot more people would be playing them. If the campaign were better and less linear then people might be playing that. And if firefight wasn’t just “spam explosives and kill grunts” then it could be a lot more fun. I would love to see a tactical firefight. There was firefight classic but did that get removed? I can’t find it anymore. Also, some kind of online leader-boards would be cool, not just with your friends.
Lastly, and this is no surprise to anyone, the AI in Reach was horrible. I just got ran over by Kat about half an hour ago. Not to mention all elites seem to do is dodge. It’s a very cheap way of making them hard to hit, they don’t do things like flank you and hide behind walls very well.
Just my thoughts.