ET clones seem to be surprisingly thin on the ground once you get beyond the couple of famous ones. I've never heard of The Aurora Encounter so that's a great one to seek out.
I'm a huge fan of Weng Weng so Double O will feature heavily! Zombies too, but it's kind of tricky laying out a simple timeline of influences. Same goes for slasher movies. You want to say Halloween kind of inspired everything that followed (not saying it was the first slasher, just the one that blew the genre up and became a template). But Friday the 13th kind of popularised just as many slasher tropes (the isolated location, revenge as motive, elaborate kills becoming the entertainment). But even Sean Cunningham admits it was a rip-off of Halloween itself... there's a lot to chew on.
There are a few others here for me to check out too. More are welcome but thanks for this little lot.
For awhile now I've thought ET itself may have been a ripoff of
The Cat from Outer Space (1979.)