Many of the above suggestions are good, but I do think (as does Stephen King himself) that The Stand stands apart from the rest of his novels.
That isn't to say that his other novels aren't good. Some of them are very good of course. But every author has his best work -- and for Stephen King -- that's The Stand.
I thought The Dead Zone was his next best, personally.
I think Stephen King is at his best when the heart of the story is not the supernatural, but how it is that the supernatural interacts with the "real world". In The Stand, it isn't the Walking Man and that whole aspect of the story which is the most interesting, rather, the most interesting element is the plague itself and the end of the world in a biological apocalypse. The central conceit of the story is that the reader imagines himself/herself not among the dead -- but among the fractions of a percent of the living in that post-apocalyptic world. That's where the story works best, because the whole danger and premise seems more real and believable. Devil worshipers in Los Vegas and the Hand of God setting off a nuke to wipe them out? Not so much.
In The Dead Zone, the ability of the protagonist to see the future is of secondary importance to the interaction with that ability and the fate of this world in the hands of a nutbar President. That's a danger we can all accept as real, so the novel has a greater impact because of it.
The creepier and odder Stephen King's plots move away from that interaction with "The Real", the less interesting King becomes.