What services MUST IT do right?
When you think of good IT services, what do you think of? As an IT manager, you probably think of different things than a business manager. So what does IT have to make sure it does right to keep the business side happy and enable IT to spend time innovating rather than fixing sub par services? It comes down to a funnel-type shape hierarchy of systems within an organization. At the top of the funnel are user machines and networking. Once those two things are running correctly, the next piece of the puzzle is file serving followed closely by email.
User Machines
If a hard drive dies or a monitor goes on the fritz, IT support needs to get the user back to work as fast as possible. In my organization, we keep spare laptops in the event of a machine needing to be taken down for repair. If a user has a performance issue with their computer or needs assistance with getting an issue fixed, that takes first priority assuming there aren't other organization-wide emergencies going on at the same time.
Networking
Unless your organization is still in the days of SneakerNet (Wikipedia), a user's machine is just about useless if networking is non-functional, unstable, or otherwise underperforming. The network performance is only at the same level as user machines because it is somewhat of a chicken and egg scenario. If a user's computer is working but the network isn't, they aren't going to be effective. If the networking is non-functional, the user's not going to be very productive because they cannot reach the organization's server-based applications. Since networking usually impacts a whole group of users, it gets a bit higher precedence than user machines. Security including virus protection, intrusion detection, and intrusion prevention also plays a role here.
File Serving
While large organizations may not use traditional file serving via network shares on servers, they definitely have some sort of document management system that users need in order to access important files. Even if other services are offline, users can usually get work done if they still have access to their primary file server. The CEO can work on his PowerPoint presentation for his next meeting. The paralegal can keep working on the licensing agreement that is in the works. The accountant can still work on the layout for his quarterly report.
ERP, CRM, and other systems
Depending on the organization, there are going to be other IT services that need to be running in order for people to perform the basic functions of their jobs. Depending on the organization, these might be added to the funnel of items that absolutely must meet at least some minimum service level. Determining the hierarchy of priorities for systems can be determined by examining the processes that drive the business. In an organization that is focused around manufacturing, raw materials, and delivering orders, keeping the ERP system operational is going to be vital. In highly automated environments, a shutdown of the ERP system could mean a halt in the manufacturing process. Not every organization is going to have anything below file serving in the funnel, but some might have several.
Once IT has these services running in a stable environment with the day-to-day functioning largely taking care of itself, it becomes possible to spend time doing innovative and creative work. If IT is spending all its time keeping the network from going down or cleaning up user's systems, they are not going to be able to spend time directly impacting the products and services that the organization offers.