Search engine optimization is very important when selling on eBay. eBay has stated many, many times how to place higher in search. All of this information is on the eBay help pages, has been discussed on eBay webinars, or on eBay Radio.
eBay sets the criteria for what gets a listing to the top of search, and if you don't know what this criteria is and aren't doing the things they suggest, buyers won't see your listings, and your sales will suffer.
Here is a quick video that explains more.