What is the best rice for sushi?
According to Seductions of Rice (which also has the best written instructions for making sushi rice I've seen), any Japanese-style rice will work fine for sushi rice.  They further define Japanese Rice as Japonica short rice which has a length:width ratio of 2.5:1.  The grains should look translucent and rounded, sometimes with a small white spot at one end.

For example, I personally use "Akita Komachi" organic rice.  This is also a "half-brown" rice, which gives it more vitamin content than pure white rice, as well as a nice nutty flavor. 

According to them, Japanese rice is frequently covered in talc or powdered starch to keep it dry, which is why rinsing it prior to cooking is essential.

I'm not going to go through their entire instructions for preparing sushi rice -- you can borrow the book from your local library for that -- but I will go over the essentials to make sure you're not missing major steps:


Rinse the rice
Soak the rice in cold water for 20 minutes
Cook the rice
Mix the rice with vinegar, sugar and salt
Spread the rice out in a wide pan to cool
Make sushi within 3 hours.