Well, as far as the Halo Combat Evolved Anniversary Edition goes, I think they did fine, and I like it. They didn't change much and all that I could see was an upgrade in the graphics which was cool. Halo 3 and Halo 3 ODST I thought were good games, but, I do admit to liking ODST better than three, because you finally got away from the Spartans and got to play an ODST.
Plus, Nathan Fillion (Malcom Reynolds from Fire Fly, and Rick Castle from Castle) voiced over the leader of the group, Gunnery Sergeant Buck, which I love Nathan Fillion so, there's another reason I love that game, lol. I tried Halo Wars but, I could never progress in it so, I just gave up on that. Never was really good at RTS games anyway.
Reach on the other hand was and still is awesome in my opinion. Not only do you get to customize your armor but, you have armor abilities, which are cool. The story I thought was ok but, that kind of goes without saying for the whole Halo game series. Again, just my opinion. I think the online multiplayer is a bunch of bull when it comes to earning credits to unlock armor pieces but, it is fun playing and killing other players. Not so fun when you're being killed though, lol.