Dinosaurs
I think we like dinosaurs because they make us feel small. Not small as in futile, but being reminded that there are bigger things out there, like when you look up at the stars at night and think about the universe.
I think we like dinosaurs because of the wow factor. What could be cooler than a planet where the apex predators were three-ton meat-eating reptiles? They look almost like aliens, aliens from our home planet.
I think we like dinosaurs because of the aura of mystery that surrounds them. We still aren't really sure what they looked like. Chances are they weren't all uniformly green and scaly. What could be cooler than three-ton meat-eating reptiles? Three-ton meat-eating reptiles covered in feathers, that's what. Imagine what a T-Rex would look like crossed with a cockatoo.
I think we like dinosaurs because, at the base of all of it, we're all still five somewhere on the inside and, well, dinosaurs!