Depends on what you need in terms of looks and sharpness. From what I hear, in Leica the pre-Aspherical 35mm give better out of focus areas (boke) but not necessarily as much sharpness as the new 35mm Asph. They're all kinda of expensive. More members would probably know more about all the pre-asph types of 35mm. I've got no idea about the 35 f1.4, other than that they're even more expensive.
On the third party side, there's the killer Zeiss Bigon 35 f2. It seems to be as sharp as the 35mm Leicas. It's a tad on the big side though. There's also the soon to be released 35 f1.4 Voigtlander. No one knows what this will be like, however it's been speculated to look like the one of the pre-ashp 35 leica's in terms of boke due too it's glass arrangement.
There's also the Voigtlander 35 f1.2, beast of a lens but people swear by it. While good, I don't think it makes much sense anymore with the new 35 f1.4 Voigtalnder. Having your viewfinder blocked really sucks to be honest, and it kinda defeats the purpose of a rangefinder when you're not seeing half the frame cause the lens is in it.
Finally, the 35mm I own is the Voigtalnder 35 f2.5 Screw mount version. Cheap, small and sexy, I like it's sharpness and boke. Check out my gallery for some samples from that lens.
Of course the best thing to do is pick the lens you can afford! If you're new to rangefinders I think spending 1-2K on a leica is a waste when a Voigtlander or Zeiss will do you very well for a fraction of the cost.
Of course, look in the gallery for members photo's and decided for yourself.
Good luck!
-Tim