"Hu Aharon Umoshe" (6:26); "Hu Moshe ViAharon" (6:27) Rashi points out, that there are places where the Torah places Aharon before Moshe and there are places where it places Moshe before Aharon. This is to teach us that they are of equal significance (Shkulim Haym). The obvious question is, how can we say that Aharon was equal to Moshe? Doesn't the Torah say that there never was or will be a Navi as great as Moshe?
The Maskil L'David answers, at this point they were of equal significance. It was only after Mattan Torah where Moshe was alone for 40 days and nights with the Shechina that he elevated himself above Aharon.
R' Moshe Feinstein offers a different answer. Of course Moshe was greater than Aharon even at this point. They were of equal significance in the aspect that each one of them fulfilled his Tafkid (potential) in this world. Hashem does not look how great one is, rather if he was able to "be all that he could be". If one reaches that level, he achieved the highest level. Aharon reached that level; therefore in this sense he was as great as Moshe who also reached the level of fulfilling his total potential. This is a comforting thought for all of Klal Yisroel. We too have the potential to be as great as Moshe in this sense.