High-end PC specifications change each year as new equipment comes out. As of 2014, any computer with a AMD Radeon HD 7730 or higher, or NVIDIA GeForce GT 610 or higher is considered a high-end computer.
There are many factors to assess PC specifications of competing brands and models. Graphics cards are relevant, as machines with higher-end graphics cards are more likely to have include other high-performance components. Comparing processors is a good idea, although different series of the same processor exist on the market at the same time. For example, as of 2014, Intel has i3, i5 and i7 processors, but each year a newer series with slightly higher specifications comes out.