These two are generally considered to be the best adaptations of King novels. Not the most accurate, obviously, but the best. I thought about adding The Dead Zone to this conversation, the The Dead Zone is different. It's not really a horror/psychological thriller that's designed to scare like Carrie and The Shining. It's more of a sci-fi thriller.
The Shining is absurd... visually arresting (it's a Kubrick film after all) but basically comedy otherwise... Nicholson is utterly ridiculous in the film Carrie is okay, Piper Laurie is great in it I'd rather watch The Shining because it's funny and great to look st
King wanted Christopher Reeve instead of Jack. If you've ever seen Death Trap... Superman could habe pulled off the psycho role very well.
Can't remember anything about Carrie except the bucket of blood over Carrie's head and the shock-ending.