16x is the max speed the device is capable of. There are many factors which will keep you from reading at that speed. Your hardware, CPU, memory, disk drive, FSB, transfer rate, etc. will all affect your speed. Also, it depends on the type of DVD you are trying to read. A single layer DVD will read much faster than a dual layer. Also, if you are reading a copy protected DVD and trying to de-crypt it, the speed will be directly proportional to the speed of the CPU, FSB, IDE transfer rate and disk speed. Some people report that they can read at close to 16x and some people say they can only read at 1x-2x. Without knowing what your system hardware is, and what type of media you are reading, it's difficult to give a definitive answer. If you are getting 10x read speed on a movie DVD, I would say that your DVD-ROM is functioning just fine.
