Matterhorn was built in the late 1950s and is the world's first steel-tubed rollercoaster. Apparently Walt hated how the sky lift tower was exposed and stood out in his park so on a trip to the Alps he realized he wanted a replica of the Matterhorn to give that area of the park some aesthetic value as it was just a dirt lot with a steel tower in the middle (to supoort the sky lift).
Matterhorn was probably never built in MK was that it is not a terribly efficient ride with getting enough people on it every hour and also the cost would have been huge to build the steel mountain again back in 1971 when MK opened. After that they just moved on to other attractions and parks and never got around to building one.
I like that Matterhorn is a one-off ride and I think DL up against MK, park to park (not including the other parks) MK has nothing on DL.DL has major things over MK but MK really has nothing over DL, all the advantages to MK are that it has more surrounding parks to visit.