Iceland is significantly greener than Greenland. Despite its name, Greenland is largely ice-covered, while Iceland has substantial vegetated areas.
"Greenland" was a marketing ploy by Norse explorer Erik the Red (~985 CE) to attract settlers. The name was aspirational, not descriptive.
Iceland's coastal climate is subarctic oceanic—cool but moderated by the North Atlantic Current. Greenland's interior is polar; even coastal areas are colder and drier. Iceland's "green" reputation is well-earned; Greenland's is historically ironic.