I actually love the Reach look, and wish that they would have just updated that for the rest of the games. As for the story...I don't mind, seeing as I never read the books.
I like 5, but I have never played it, and I certainly do not think it is bad. 4 seems good, and 343's desperate attempts to bring the expanded universe into the games is commendable, but handled poorly. I also don't really...like the Forerunners and Prometheans. But they are not bad.
Seeing as I have not played many games, and only one Halo game..take this all with a bucket of salt.