Okay, let's be real strict and only do the 18 attractions that were ready to operate on Sunday, July 17th, 1955.
We'll use the same color code;
Red for Disney IP attractions,
blue for corporate attractions, black for everything else. And even though King Arthur's Carousel was based on the rights to the movie The Sword In The Stone that Walt purchased in 1939, we won't count that since Walt didn't release the movie until 1963, so it will be black.
Disneyland & Santa Fe Railroad
Main Street Cinema (showing vintage silent films, not Disney cartoons)
Horse-drawn Streetcars
Richfield Oil Autopia
20,000 Leagues Under The Sea (based on 1954 Disney film)
American Motors Presents CirCARama
Crane Bathroom of Tomorrow
Jungle Cruise
Mark Twain Riverboat
Davy Crockett Museum (based on 1955-56 Disney serial films and pop-culture fad)
Stage Coaches
Mr. Toad's Wild Ride (based on 1949 Disney film)
Peter Pan's Flight (based on 1953 Disney film)
Snow White's Adventures (based on 1937 Disney film)
King Arthur's Carousel
Dumbo the Flying Elephant (based on 1953 Disney film)
Mad Tea Party (based on 1951 Disney film)
Mickey Mouse Club Theater (based on 1955-58 Disney TV program)
That's 18 attractions, and 8 of them were based on Disney Intellectual Property, and almost all of that IP from the early to mid 1950's. That's
40% of the attractions based on Disney IP on opening day!