The venerable Canon EF 50mm f/1.4 USM is a great value and a staple in my equipment bag. It is well built, light weight and provides very good image quality. Its more expensive cousin, the EF 50mm f/1.2L is a different story. It lists for almost 4 times the price of the former but does not provide even 50% better in IQ.
Sigma has been announcing very competitive Art prime lens in the last couple of years and is planning to release more glass. Their 50mm f/1.4 Art lens announced last year received very good reviews.
Recently, Canon announced their EF 50mm f/1.8 STM lens. It is a low price but not low quality lens that is well suited for taking videos as well as stills. Both the EF 50mm f/1.4 and EF 50mm f/1.2L are in line for an upgrade. Last month, Canon announced they have perfected the Blue Spectrum Refractive Optics technology and released their first BR prime lens, the EF 35mm f/1.4L II. I will not be surprised if Canon release an upgrade to both 50mm lens next year.