50mm's render the world with no expansion or compression like wider or longer lenses do. They see things how they are and some will see that as boring. While the 50mm to me was the only lens I grew up on, (Minolta Maxxium AF and a 50 1.8 ) so It grew on me for good time.
After a while, It changed the way I composed things because there was no perspective tricks. I composed according to balance, shadows, rhythm, negative space, color and the other more important things in a photo. Thats what the 50mm does, it shows you how you compose your images based on these more important things.
As for lenses, Any of canons offerings are good but the 1.2L is the best.