There can be an argument made for several. Whereas it is true that it is specifically stated in CoP that Walt personally liked it, none of the other classic attractions have small documentary spiels before talking about the creation or history of the attractions. Perhaps if Pirates or Small World had that, they'd also discuss Walt's love of the attractions.
That being said, Walt Disney always did love trains in general. One of his two windows on Main Street, the most obvious one, is on the center of the Railroad Station just as you walk into the park. I do think he had a strong passion for CoP, but I could arguably see that represented in other attractions as well. He had a great love of trains though, having one in his backyard, and having even gone to train conventions. Usually, when Walt was photographed on a ride, it was as the conductor of the train, and the way the parks are set up, the train has the most prominent positioning.
It could be argued trains are scattered globally across the world, and aren't generally that unique, whereas many of the Disney attractions can only be found in Disney parks. Walt Disney World's train is not Disneylands train, nor is it any other train. The Carousel of Progress today is not an exact copy of what Walt built back for the 1964 World's Fair. The very nature of CoP is that it'd evolve and change. Walt actually may not be as impressed with the ride now, as the company hadn't put the attention to it that he envisioned. Back in the day, people envisioned flying cars, but we're a long ways away from that. CoP allows you to imagine and envision where society is going and how it can improve, by looking back on what mankind has already done and accomplished in terms of problem solving. Walt may have loved that concept, but been disappointed that the world didn't evolve the way we dreamt it would back in the day. It has evolved in other ways though. In 100 years man went from never flying, to putting a man on the moon. It's amazing to think, but Walt died before Armstrong stood on the moon, but Walt envisioned that happening just as Jules Verne had. And, possibly someday, man will stand on Mars, but it's a long way off.
That being said, at least it's still around, and is pretty close to what it was back in 1964. For any physical attraction that didn't exist when Walt was alive, it's nothing but a guess as to whether he'd like it or not. That being said though, many of the attractions that were there when he was there have changed, so they aren't really the same thing as what he may have appreciated. Walt Disney World may have changed this, as the monorail became a method of sizable distance in Disney World as apposed to Disneyland's version. With Walt's love of progress and trains, he may have loved that, though he passed away before it was ever completed. I think it's safe to say most of the rides we envision as classic attractions, Walt appreciated. If I had to guess, I would suspect Walt liked Mad Tea Party, Dumbo, Matterhorn, Peoplemover, and others, but have never really heard a discussion involving them one way or another. Kilimanjaro Safaris is actually what Walt originally envisioned for Jungle Cruise, except it uses a jeep and not a boat. It's tough to say with anything new as to if he'd like it or not, but technically CoP and many others aren't the attractions Walt completely witnessed.
