Why didn't Naruto's Rasengan beat Sasuke's Chidori? According to Kakashi, there are 5 fundamental chakra natures: fire, wind, lightning, earth, and water. Each nature is superior than another, and inferior to a different one.



Focusing on wind and lightning chakras, Naruto's only nature chakra is wind, so the Rasengan must be a wind-type jutsu. Chidori, of course, is lighting. Kakashi said to Naruto that, using wind chakra, he cannot defeat Sasuke's fire abilities, but against lightning, wind can easily beat his lightning jutsus. 

This leads me to my question...



In the Naruto series, there are many occurrences where Naruto clashes with Sasuke. Their battles always end with a Rasengan against Chidori blast.

Since Rasengan is generally wind-type and Chidori is lightning, shouldn't Rasengan easily beat Chidori? I can't imagine how a lighting style jutsu can match, even beat a wind-style jutsus. Maybe Kishimoto accidentally forgot about wind's superiority over lightning, but I just want to ask: can someone explain?
The standard Rasengan has no natures associated with it.  It was originally based on the Tailed Beast Ball, which is simply a dense amount of chakra directed at a target.

Eventually, Naruto adds his wind nature to Rasengan, which, in turn, creates several different variations of it.  But neither of these variations are being discussed.



However, this doesn't mean that either Chidori or Rasengan have a direct type-advantage over the other.  At that point, it becomes a matter of the abilities and strengths of the wielder, and as we now understand it...


   ...it ended in what could be seen as a draw, with both Naruto and Sasuke losing the arms in which they perform the jutsu for their final fight.