I'm going to limit my criteria to Universal Orlando, and only rides that currently exist and aren't defunct. With Epic open, there are a lot of new options to choose.
In my mind, it goes something like this.
1. E.T. (Represents the classic and earliest era of UOR. The only remaining ride from that lineup, and one that is exceedingly wierd, creative, and enjoyable to this day.)
2. Amazing Adventures of Spider-Man (One of the best attractions ever built. Eternally enjoyable, incredibly paced, and remains the best Marvel attraction ever built, well over the competition in Mouseland. That rivalry between the parks feels notable to represent in some way.)
3. Hagrid's Magical Creatures Motorbike Adventure (You can't have a Universal Orlando Rushmore without Potter, or without a rollercoaster. Both served to dig them out of the pit they were in through the 2000s, and were fundamental to building the resort we see today. On top of all those deeper reasons, this coaster itself is also just highly innovative, intricately themed, incredibly unique among other Orlando coasters, and just a really exhilirating good time.)
4. Monsters Unchained: The Frankenstein Experiment (A bold new showing of incredible animatronic and screen technology at the top of their craft, using the most classic IP in the Universal library. What was once nothing but a pipe dream in superfan's minds for a UCM Land was actually brought to life in a way that finally, after countless attempts, improves on the model Spider-Man originated 20 years earlier. Just an incredible ride. In my mind, the perfect one to encapsulate the old and new of Universal Orlando.)