I mean, the thumbs help hold stuff, sure, but it's our large pre-frontal cortex that really comes in clutch. That and our penchant for violence. There's evidence to show that the Neanderthals were possibly more advanced than us before they "died out," but also less violent and selfish. It's those traits that led us to kill them or cut off their access to resources while we took them all.

We are still animals. Any biologist will tell you that, but that's not a negative thing, it's just a facts. It's like saying we're mammals. It really comes down to how you define "better." and "successful." Obviously, we are making those determinations from our point of view, so we tend to define them with the things only we do. But if we're defining successful by technological advancement or the ability to do advanced math, or even versatility in abilities, we're at least top 3. But those orangutans are pretty nifty with their use of twigs sometimes, so don't count them out.