i don't think that the rinengan is supraestimate.....nagato's case was different...the rinengan is bot nagato's, so he can't use the full power of rinengan..is like kakashi's case..he can't use the mangekyo for long time like obito, becose that eye dosen't belong to him. just think thet the rinengan created the moon, and madara showed just a little part of the rinengan's abilities...we don't know how powerfull this doujutsu can be.