Norton is not junk, but it is very system resource intensive. It's detection rate is among the best. Because it is the big boy on the block, it gets a lot of undeserved bashing (like Microsoft).
Is it the best? No.
Avg and Avast are both excellent free AV programs, because they offer virus scanning and real time protection. They trade off as to better detection rates, but both are close. Seems the last head to head I saw had AVG with a better score, but last fall it was Avast. Another worth considering is AntivirusPE, especially if you have an older machine, since it's memory footprint is the smallest of the three, but it does not offer a realtime mail scan.
If you are willing to pay, the two best AV programs are Nod32 and Kaspersky, which consistant rank 1 or 2. Kaspersky tends to be more system resource intense than Nod32, so many prefer the latter.