Basalt is actually the most common extrusive igneous rock.

Intrusive rocks form when magma cools and solidifies beneath the Earth's surface. Examples of intrusive rocks include granite, gabbro, and diorite.

Extrusive rocks form when lava erupts onto the Earth's surface and cools. Basalt, rhyolite, and andesite are examples of extrusive rocks.

So, while basalt is very common, it's not the most common intrusive rock. Granite is generally considered the most common intrusive rock.