The ones who should be sued by the Enron stock holders are the audit firms that signed off on their financial statements. They were asleep at the switch.
If people bought Enron because an analyst recommended it, it was a hot stock, a market maker or a leader on the Internet, then finding the person at fault is a simple process, look in the mirror.

The smooth transition of the marketplace to the post-Enron era proves the vibrancy of capitalist in the US.