That's the true! No matter how you motivate and stimulate them, they will never will perform like the founders in long run. And this cannot and shouldn't be expected from them. They care about what's their job like today! They won't sacrifice for long run.
Founders are another story. They work tireless days, nights, during weekends putting on risk family relationships, friendships and even their health. But the bet is a way different. Success could bring them a fortune.
On the other hand success will bring a bigger salary, bonus, maybe shares to employees. No matter how big these are they cannot compete with the benefits of the founders. That's why there will always be difference between founders and employees.
In software business is normal to have 2-3 guys who makes a small company and create first version of the product. This version is created in no time - everyone in the team knows all the details and work on them no matter of the clock. And when this version is a blockbuster and it is time to hire some hands to help on next one the expectations are so high. Performance will never be the same.
Note: I am not saying that it is bad being an employee or a founder. Each situation has its own pros and cons :).
(These thoughts are inspired by Joel Spolsky's article "How Hard Could It Be?: Lessons I Learned in the Army")