Quickbooks would be ok for a smaller family owned busines. It's easy to learn and there is a lot of online help.
For a medium sized business, it depends upon what type of business - service or manufacturing...Microsoft Dynamics GP or SL would be good software to look in to. This software allows for multiple users and is good for a company that is growing.
A large business can mean so much - do you mean large like General Electric? Large like Comcast? Most companies like that would use Hyperion or Oracle GL.