Why did Skype succeed where Net2phone failed.

They got customers and kept them.
Actually it appears that Net2phone is still in business, so I looked further.

Net2phone started in 1996, Merger with IDT feb 06, alliance with Telefónica May 06.
Is a public company based in the USA.

Skype founded in 2003 based in Luxembourg. They have relationships with a large network of hardware and software providers. And are owned by EBAY.
EBAY is probably the biggest factor in both their stability and their continued success.

I used Sunrocket, quality service and great price, but they didn’t manage well and debt forced them out of business. But unlike Net2phone they actually went out of business.

Skype has a cooler name.

The statement “Skype has a cooler name” isn’t actually so far off. Skype was the first major VoIP provider to explain the concept to customers in a practical way, and to make the service feel like a vision as opposed to a feature list.

Net2phone market in a business manner, citing reduced call costs, recording and conference calling as their main features, while Skype approach customers with the idea that they can call friends on the other side of the world for the same price as calling the guy at the end of their street (or for free if they have a computer with an Internet connection).

Skype win simply on branding and advertising, as they don’t just provide a service — they know how to talk to their customers. For more evidence, observe the difference in user experience on http://skype.com/ and http://www.net2phone.com/ . The homepage of the Net2phone website (after you get past an ugly and unnecessary country selector that makes you feel stupid for living anywhere but the US) barely even explains what VoIP is, or how it will be useful to you. “Consumers” is not a friendly word to have to big on your homepage, and Skype understand basic concepts like this.

http://skype.com has a free chat software http://www.net2phone.com does not have it, i use http://www.switch2voip.us because of the support, overall they are all the same if you just want to make calls.