Egyptian cotton is widely considered to be the best quality cotton that's available on the US market today. It's unrivaled in terms of its durability, comfort, and breathability when compared to not only other types of cotton, but also other types of fabrics, including both synthetics and other natural fibers.
If you're looking for a comfortable bed sheet that's going to last you for over a decade and maintain its quality, real ELS Egyptian cotton is definitely what you're looking for. The best brands, though, can be difficult to tell apart from general brands that are misrepresenting their products as something they are not. Real Egyptian cotton sheets that are high quality aren't generally going to cost under $100 a set, but they can range as high as $600+ for a single set, depending on the size that you want.
The best brands of Egyptian cotton sheets can be found here: http://luxuryofthepharaohs.com/best-egyptian-cotton-brands/. What you're really looking for is the “ELS” specification on your sheet labels. Any company that produces sheets in Egypt can claim that they're “Egyptian”, but only those that use extra long staple (ELS) cotton are the quality that's usually associated with the “Egyptian” label. Brands often misrepresent their products by saying that they're Egyptian, but not specifying that their products aren't made of ELS cotton.