Greenland had no native population (or at least no native population in the area the Norse settled), at the time the colonies started, the Inuit only arriving (in the area) later, which given subsequent relations undoubtedly helped the initial success of the colony.
While the colonists came from Iceland, most of Greenland's subsequent trade was ultimately with Norway, in part because neither Iceland or Greenland had much timber for shipping, and in part because they largely demanded the same things. Its not clear if ships destined for Greenland tended to stop at Iceland on the way, but a few references seem to suggest that a fair number didn't.
Regarding Vinland, well its probably informative that it was abandoned after 10 years, while the Norse persevered with Greenland.
@olverki. A rather large problem with your thinking is that the population and resources of Norway, Iceland and Greenland were not equal to each other. You probably should take the time to consider that the last was desperately poor and ultimately failed. Neither Iceland nor Greenland were self-sufficient and depended on trade with Norway for some essentials notably timber (in the case of Iceland after a fun experiment in deforestation) and iron (by the end of the Greenland colonies' existence iron is near-nonexistant so no iron weapons etc).