Okay here is my balanced opinion of the two future games considering I have played both big hits (halo 3, cod mdw2).
Halo Reach: It is important to play the game because it tells you the
backstory of the Spartans and how the Covenant came into the picture.
The Campaign looks intense, but the multiplayer is certainly different.
It isn't really hard to adjust to it though. All the weapons now have
recoil, but at the same time the shotgun, hammer and grenades seem
overpowered whereas the sword has been weakened. Other weapons such as
the DMR require more accuracy than past games as it takes four body and 1
head to kill someone (i think?). Anyways, the loadouts are quite
enjoyable whether it be sprinting, flying, stalker, or armor lock. Armor
lock is annoying if an enemy is using it because it either prevents the
unavoidable (meaning there is nobody there to save him) or he does get
rescued and you die. In any case, there play is more team based rather
than individual. I also think that Invasion is a lot of fun, although I
do hate objective based games.
Black Ops: I did not play the beta (being that there wasn't one and am
taking this based on playing mdw2). I liked the realism of the game.
Everyone in the game looks real, the weapons are real, etc etc. It
definitely depicts war in the right direction. The only thing that I do
not like about it is the camping involved in it. I know that is
definitely an aspect of war, but I hate how I will be walking up the
stairs and someone will be there and shoot me. Then I will go around
that way 2 minutes later and he will still be there waiting to shoot me
with the akimbos. The campaign of the series, I believe, is more
interesting than the Halo series for the most part. I think Reach's is
probably the most interesting one to date, but the Call of Duty
franchise has made a superb Russia vs U.S. series.
I prefer Call of Duty Black oops.