Well I think we can agrea to disagrea atleast on the first part of what your saying, scifi and fantasy flicks hinge not only on a good story line but the quality of the effects in them wich is why everything that the scifi channel has put out except for the modern BSG has fallen flatter than week old soda. There are ofcourse movies that dont need to be remade for better effects, one that I can think of that was a sleeper horror thriller was called shockwaves and had no special effects to speak of. Special effects did good for most all of the latest king kong except for the stampede wich was mimicked in its style in the recent indiana jones with the side by side jeep run.
I disagree with this as well. If the story is well written and compelling, it doesn't matter if the effects are the latest CGI or some guy wearing a fishbowl on his head.
Creature from the Black Lagoon, Forbidden Planet, On the Beach, War of the Worlds, Silent Running, Planet of the Apes, 2001, etc. All these films have inferior graphics and effects, yet they all are watchable on repeated viewings. Everyone that has been remade has been a disappointment.
A great example is The Thing/The Thing From Another Planet/Who Goes There. It has been remade several times and, in my opinion, is weaker with each retelling. Nothing touches the original for the suspense generated. Of course, nothing even comes close to the original novella for pure terror.
I think that's the key. Special effects have replaced suspense and tension as audience tools. I am an old fart, but I prefer the earlier mechanisms.