Your competition are hotels who offer similar products and who are seeking similar markets. These are actual hotels that you need to initially identify, and then compare strengths and weaknesses of each property as they compare to your property. What are the points of comparison that potential guests would look at?
One way to start is to visit www.hotels.com and search your hotel's city for geographic competition.
Keep in mind that your hotel may also compete with other destination/conference hotels outside your geographic area.