Humans have certainly had a profound effect on their environment, but our current claim to dominance is based on criteria that we have chosen ourselves. Ants outnumber us, trees outlive us, fungi outweigh us.
Bacteria win on all of these counts at once. They existed four billion years before us, and created the oxygen in the atmosphere. Collectively, bacteria outnumber us a thousand, billion, billion to one, and their total mass exceeds the combined mass of all animals.
They have colonised the entire planet, from the stratosphere to the deepest ocean, and despite all our technology, antibiotic-resistant bacteria continue to kill hundreds of thousands of us every year. When humans are gone, other species may take our place, but bacteria will continue to dominate the planet.