Lots of things I agree with, so I'll highlight:

In terms of campaign, I like the idea of branching campaigns. Failing to complete a mission in time or a certain way doesn't mean failure, it just means the game changes. This generation of console however, branching campaigns I think would still be canned experiences since there is little overhead available for a branching AI.

I agree with the open world concept of ODST translated to a "regular" Halo game, though in the setting we're talking about I'm not sure that'll be possible. Certainly something more compelling than a maze, as Halo 1, Halo 2, Halo 3, and Reach have been. If back story can be integrated into the campaign to make it even more interesting in a less subtle approach than terminals, that'd be good too.

I prefer Halo Reach multiplayer over Halo 3's multiplayer, but the maps need to be bigger and more varied. Not sure what the hang-up is over power-ups. It goes back to Indiana Jones, "You must choose, but choose wisely." Some people just don't pick the right power-up for the style of play. invisible while you're running around is like asking to be killed.

Reach introduced upgradeable armor to the player character's look. Those upgrades should now have an impact in the game in Halo 4. They shouldn't be XP-unlocks in the campaign, they should be collectibles found and integrated into the standard armor. The same could exist for weapons as well. For those who complete the campaign, find all the upgrades, they'll end up having a bonus when playing multiplayer. Collecting all the armor and weapon upgrades will translate into earned XP in multiplayer, thus making the next upgrade easier. For those who just jump into multiplayer, they'll have to earn a lot more XP just to work up to the level of those who complete the campaign, not to mention they don't get the upgrades available from the campaign. Which may also limit what upgrades are available to them in multiplayer. Integrate Halo Waypoint even more so than it was in Reach and offer more stats in Waypoint.

Bring back the epic story of Halo. ODST and Reach were nice as filler stories, that is they filled in blanks, but they did little to propel the story forward. Halo 4, while reaching back into the Halo saga, will also have to move the story ahead into the current timeline, whatever that may be. When I finish Halo 4, I want to sit there and wonder about what just took place in the game. What did I learn from this adventure? "That was cool," or "That was interesting," won't cut it. Reach actually had a pretty good story, but it was anti-climatic. It didn't allow me to wonder what happened to the characters in the game, because well, they died. Even the character I played as. The story has to have a great hook. Even better than Halo CE's.

I want huge online battles......like spartans vs covenant(or whatever the new enemies will be) wars

and How about being able to be the enemy against other players like in Gears3

The formula is basically perfect as is. Sprint needs to be a default ability. More character customization for online and bigger battles perhaps. I'd like to see dual-wielding return as well. Anything beyond minor tweaks at this point and they'd run the risk of losing that Halo feel.

There is a lot of wasted potential in terms of visuals and storytelling in this franchise. If the game gets unveiled and it looks like Reach I'm gonna be mad. It deserves Gears 3 level graphics. I won't hold my breath for a really great story but that, in my opinion, would really elevate it to GOTY quality.

Trust me he won't, he only got Reach and Anniversary cos I begged him

I will pick up Halo 4 more than likely, but I echo Machina's sentiments, I want radical change.

still halo CE and Halo 2 were most of the time stated as the best looking games on the original xbox...  and gears of war 3 looks terrible because having splitscreen?

Lucky that you are an great player with 0.81 K/D  in MLG and 0.50 K/D in Double team...Two playlists where skill matters...  

http://www.bungie.net/Stats/Reach/CareerStats/playlists.aspx?player=ironDX 

Anyway the multiplayer system needs some change.     Let people join matching in progress,  a new punishment for quitters.  (the ban and resets suck when you have to quit because you have to go)..  . 

Any ideas as to what kind of change/what you would like changed? Anything recent that needs to be added or removed? (Perks in Halo: Reach were kinda meh in my opinion, I enjoyed the pickups from Halo 3 more).

Also, a bit of that global battle(s) idea from that youtube video someone linked, would be rather awesome in my opinion. (Albeit implemented in appropriate form and only in levels that it would make better)

Halo CE was one of the best lookign Xbox games at launch. It was far surpassed. Halo 2 as well. Look at Ninja Gaiden, then look at Halo 2.

And where did anyone say terrible? "Not the best". That means not #1, not the greatest of them all. That doesn't mean bad. Actually it can be great. Phenomenal! Stupendous! But not the very best. Like I said, they could make it look even better than Reach, but it's not going to claim the graphics title.

I just find it weird to read this discussion  when you have a game like Gears of war 3 that has splitscreen and is one best looking games and maybe the best looking game on X360 in 2011

you did not really pick one wehere he has played 18m did you? wtf? serious? i mean it's like i would see barcelona losing against some other team in the spanish football league and saying "yes they aren't as good as the rest they lost this one game"