Not necessarily. They're convenient, faster, and safer in most cases, but they're not the greatest if you want a very close and precise shave over large areas. Manual razors have been used for centuries and are still the best choice for high quality shaves, especially for professional barbers.
But if you just want a quick, easy way to manage body hair on a regular basis, there are a wide variety of electric shavers that can meet your needs and replace your reliance on a manual razor.