I'm thinking stateside on this, but three attractions come to mind. Soarin over California, Test Track, and Tower of Terror. I think of all of those, Tower of Terror is truly the best product that was much different from what Disney had created before. Soarin over California was great, but it is essentially a next generation simulator with film footage similar to those seen in many circlevision theaters. Test Track was pretty cool, but I don't know if it was mind blowing. Tower of Terror however took a drop tower concept and completely re-imagined the technology. The story, costumes, theming, music, architecture, and thrills all come together to form in my opinion on of the last great classic attractions that was built on par with attractions like Pirates, Haunted Mansion, etc.I could be biased on that though since it is my favorite attraction.
Best attraction in all of Orlando though? Well, I think I would have to give it to either Spiderman or Harry Potter over at IOA, and I'm not even a Harry Potter fan. They essentially pulled a "Tower of Terror", but it is more recent and more technologically advanced.
There have been other great attractions that have come and gone since then, but not many that are truly mind blowing!