If you have the desire to be a music critic, this playlist could be your first lesson. It contains some of the most respected and influential bands that never sold in meaningful numbers.
Truly great music usually finds consensus among critics and musicians and is ignored by the masses. There are many other bands that fall into this category, these are just the first 19 that popped into my head.
Please feel free to add more to the comments and help make this a definitive list.
If you're a commercial pop music addict who has traditionally found your music on television and radio, but are looking to expand your musical tastes. Or if you're just looking to understand what constitutes "critically acclaimed". This playlist is a good start.
If you don't get it after the first listen, listen until you do. You're musical salvation depends on it.
19. Titties 'N Beer - Frank Zappa