There are so many CRM vendors that it's useful to organize them in categories and to restrict your search to the categories that best match your requirements.
CRM systems can be mid-range or high-end. Mid-range systems have a good set of functionality and scale fairly well, but they have limited customization capabilities. They are easier and faster to implement than high-end systems. High-end systems have extensive customization capabilities and scale best, but they also require much more time and many more resources to implement. Unless you clearly need the additional functionality and customization tools of high-end solutions, it's best to stay with a mid-range tool.
CRM systems can be suites, covering several business functions, or point solutions that focus on a particular piece of functionality. Although suites deliver pre-integrated solutions, you may need to patch together several point solutions to get the ultimate best-of-breed solution.
Some vendors offer so-called vertical solutions that are customized for specific industries, while most tools are general-purpose. If you need a high-end system you will find that high-end vendors often offer vertical solutions, which should save you some customization work.
CRM systems can be purchased as packaged products or in an ASP arrangement. Some can be purchased either way. If you have reasonably limited customization requirements, need a solution quickly, and do not mind the idea of an ASP arrangement, it may be the best solution for you.