Why were the Chidori and Rasengan ever regarded as powerful jutsu? The hard part about using the Chidori or Rasengan is making contact. If you make contact, the battle (should) be over.

I don't see how having a Chidori or Rasengan is that much better than just using a kunai. Sure, a Chidori does more damage; but still, if you stab somebody with a kunai, the battle (should) be over.
The point of Rasengan and Chidori is not just to make contact, but POWERFUL contact. 

A kunai can never penetrate Gaara's shield or any other strong defences, but Rasengan and Chidori can. Oodama Rasengan and Rasenshiriken are on even greater levels because their damages are astronomical.

In the fight with Kakuzu, before Naruto came, it was incredibly hard for the others to stall out Kakuzu, let alone finish him. But with Rasenshuriken, the destructibility penetrated and annihilated his charkra system in cellular level. I don't think you can do that with a kunai.

The power of the Rasengan and Chidori is not limited to just "making contact". Charkra nature manipulation and shape manipulation comes into great meaning at this point: Sasuke can turn his Chidori into mini needles, arrows, sword (with adjustable length), and stream. Naruto can fuse his Sage charkra style into the Rasenshuriken to make it a flying disk of destruction. This can't be accomplished with a simple kunai.