Can I copy an image from another paper (that I am citing)?
You have two different questions: one in your title, regarding coping an image, and another regarding the results.

Copying a figure:

It depends on the license of the paper. If it is appropriately licensed (as with a Creative Commons Attribution license), you generally can, as long as you indicate it. If it is copyrighted, you are in the grey area of possible fair use. In these cases, the safest option is to contact the copyright holders (usually the publisher) and ask for permission.

Another option is to contact the authors and ask them for the raw data itself, so you can plot it yourself (so you keep a constant style across the paper), or ask them to regenerate it for you.

Using results:

The results are not copyrightable, so you can freely use them. If Smith et al, 2007 report an accuracy of 91%, and you get a 97%, you can freely put the numbers next to each other.