1] The medrash tells a story about some rabbis who were going from Eretz Yisrael to Bavel in order to learn. When they were leaving Eretz Yisrael they cried, ripped their clothing and said [based on the pasuk] that the mitzvah of living in Eretz Yisrael equals all the mitzvos and they turned back on their heels and returned home.
מעשה ברבי יהודה בן בתירה ור' מתיה בן חרש ור' חנניה בן אחי ר' יהושע ור' נתן שהיו יוצאין חוצה לארץ והגיעו לפלטיה וזכרו את ארץ ישראל וזקפו את עיניהם וזלגו דמעותיהן וקרעו בגדיהם וקראו המקרא הזה וירשתה וישבת בה ושמרת לעשות, אמרו ישיבת ארץ ישראל שקולה כנגד כל המצות שבתורה.
The question is that even before they left they were aware of the fact that it is forbidden to leave Eretz Yisrael [as the Rambam paskens - why it is all but ignored today is another topic....] but left anyway in order to learn Torah. So why did the fact that the mitzvah of living in E.Y. equals all of the mitzvos change their minds? Just like the mitzvah of learning overrides the איסור of leaving Israel it should also override the fact that the mitzvah of living in Israel equals all of the other mitzvos? [It is clear that it is better to sit and learn Torah in Chu"l than to live in E.Y. and not learn. פוק חזי all of the gedolim who lived in Chu"l and continue to do so until this day in order to learn and teach Torah]. What changed their minds??
2] What is unique about the various mitzvos that Chazal tell us are equal to all of the mitzvos of the Torah?
And much much more - here.