First of all, I have to say Canon L-lenses are fantastic pieces of engineering. Canon has been the marker leader for a long time now and they would not have got there if they did not build quality products. Particularly their telephoto selection is so impressive. I truly admire how they are built and how most of them perform on the field.
However regarding to OP's question: I voted without a shroud of cloud,no. One of the silliest thing is to claim that all L-lenses are automatically the best and worth the price premium over their third party competitors (wow, I hate the use of word 'third party', for example Zeiss has been around since 1846 and we still call it 'third party' ??). It's certainly not true. It depends which lens we are talking about and what does the user intends to use the lens for. Particularly Canon's wide angle selection leaves lot of room for improvements in my opinion. Where is the 12-24mm f2.8L? Nikon 12-24mm simply trumps Canon's 16-35mm f/2.8L. Canon has no match for the fantastic Zeiss Distagon 21mm f/2.8. Ok, I admit 21mm is unusual focal lenght but for my taste it's simply the perfect focal lenght for landscaping. The Samyang 14mm f/2.8 is just as good as 2000$ Canon EF 14mm f/2.8L USM II (in my view the most overpriced Canon L lens, ever). Well, apart from distortion. Fortunately for Canon the TS-E lenses are fantastic pieces of engineering and it kind of makes up for the lack of quality ultra wide landscaping selection.
Some examples of possibly equal or better alternatives for Canon L-lenses:
- Canon 135L f2 is a fantastic lens. Truly Legendary. But wait until you try the new Zeiss Apo-Sonnar 135mm f/2. It will blow your socks away, image quality and build quality wise
It's so much sharper wide open than the Canon and at first I couldn't even believe it. I also have a positive feeling about Sigma's plans to release their 135mm f/1.8 HSM OS Art lens. Interesting times for us fans of 135mm focal lenght 
- Canon 35mm f/1.4L: Sigma 35mm f/1.4 ART, Zeiss Distagon 35mm f/1.4, Canon EF 35mm f/2 USM IS
- Canon EF 50mm f/1.2L. This is possibly the most controversial L-lens for my taste. Eventually I sold it, because I concluded that I got same IQ from 4-times cheaper Sigma 50mm f/1.4. Now I am waiting for the rumored Samyang 50mm f/1.2 
- Canon EF 14mm f/2.8L USM II: Zeiss Distagon 15mm f/2.8, Samyang 14mm f/2.8
- Canon EF 24-70mm f/2.8L USM: Tamron SP 24-70mm f/2.8 DI VC USD
- Canon EF 100mm f/2.8L IS USM: Now if someone doesn't know the legendary IQ of the Zeiss MP 100 f/2.8 should go check out some image samples from this fantastic 100mm macro lens
. Though I admit that I don't really like the amount of CA from this classic Zeiss lens.But then again 100L has some CA as well...
Now regarding autofocus performance. It is true that most of Canon lenses perform better in extremely dim light compared to their third party competitors. But it's silly argument to claim that it's true for all Canon lenses. First examples that come to my mind is the lackluster AF-performance of Canon EF 50/1.4, 50/1.8 or Canon 35mm f/2 (the old one). Canon EF 50mm f/1.2L was full of problems for few years when it was first introduced. Luckily for Canon some improvements were made and the present day 50L focuses really nicely (batches made from 2009-2013 or newer). But I particularly applaud Sigma's improvements in autofocus performance with the introduction of their Art series. Their USB dock works simply flawlessly. It would be certainly beneficial for Canon as well to release their own USB-dock for precise autofocus microadjustment (variable distance), since you can make very precise adjustments for increased autofocus performance and reliability.
To sum up: I am not trying to bash Canon here. I love Canon. But I simply feel sorry for people who are so narrow-minded to think that only one company (Canon) builds quality glass. I hope I will never become as obtuse as the world of photography becomes so much more interesting when you open your mind to other classic lens manufacturers such as Cosina, Contax, Tokina, Sigma, Zeiss, Nikon and Leica
And the greatest thing staying with Canon bodies is the fact that you have so many lens options to mount in addition to their Canon counterparts 