1- Perfect being prophecy non existant in star wars, Anakin in no way is perfect only a tool, and as I know of Luke never had a prophecy about him and he more or less brings freedom to the galaxy
2- Deserts are deserts, by that rational any desert in sci fi is plagerism
3 -Its not like the sarlacc was a major player in the film I get the impression that it couldn't even move
4- This is something that has existed in mythos since the beginning of man, the fact that it could be used by all jedis and not just gods or those prophesized about actually shows a little more originality
5- Force speed though I'm sure the jedis move faster then humanly possible in the movies, is only a video game concept, I don't remember Yoda telling Luke, "Now use your force speed."
6- The importants of spice is not prominent at all in Star wars. Its not originally Dune either, lots of mythes of the spice brought from the east were established in Europe during there alchemy craze
7- The idea of the epic or prophecized twins is nothing new, Apollo & Artemis, Aegyptus & Danaus, Hercules & Iphicles, Castor & Polydeuces all greek/ Remus & Romulus roman/ Baldur & Hoder norse
Sorry if I speled any of these wrong, but as you can see this idea is by no means originally Dune
8- No need to comment very elemntary to have conflict
9- blame Joesph Campbell
10- Not much of a similarity there
11- Navy seals, army rangers, marine recon
12- Seeing with your faith sounds more christian than anything
13- It say in episode 6 that Obi-Won hid the twins from him, so its safe to assume that Vader never knew he had son till Lukew showed up and he didn't know about Leia until the fight on the Death Star. Almost certainly he didn't just miss the fact that she was pregnant, so I think that she probaly ran off after he turned to the dark side