Orcas are smart enough to give each other distinct names and seem to understand the concept of verbs/nouns when identifying human words[1]. They could very well be smarter than us, but they'd never dominate the planet technologically: their flippers have no evolutionary path to developing fingers and thumbs.

[1] Some people point out that we've never learned orca language but they've learned ours. This is true, but it's also true that orca scientists have never kidnapped human children and intentionally tried to teach them orca language. So it's more of a poetic comparison than a scientific one.