Hi Mdr,
well as with all things there is never an easy answer. Canon currently make four 50mm lenses, the 1.2L, 1.4, 1.8 and the one you missed from your list the 50mm f 2.5 macro lens. The macro has a lot to recommend it, also the MTF chart for the 2.5 is if anything slightly nicer than the 1.4. Photodo rates the 1.4 and the 2.5 at 4.4/50 which is a very respectable score. If you want to do some close shooting ir a bit of macro (only goes to half lifesize) then you may like to thing about the 50 2.5 compact macro.
Having said that, I like the 1.4, have the 1.0 and have used the 1.2 and will be keeping my 1.4.
All the best
BearSummer