I've heard a lot that making Aliyah to Israel is really good, that it's a mitzvah and even that it's an obligation if you can. But how important it is to make Aliyah? Could you give me references/quotes?
Rabbi Moshe Feinstein ruled that there is no obligation to move to Israel nowadays, but if one does they fulfill a positive mitzvah of the Torah. See Igros Moshe, Even Ha'ezer (a), page 253, last paragraph of responsa 102.