I might agree with you except for one remake that gives hope to the entire concept of remakes (which is good, since they're all hollywood makes anymore.)
The '82 remake of The Thing.
Original Version: Frozen space dude wakes up, gets electrocuted.
Remade Version: Scariest movie of all time. It taps into just about every human fear, and does so in a believable way. I could write many paragraphs on it, but I think it speaks for itself.
As for the worst remake, I'd say that just about every other SciFi movie remake ties for this place.