Sad days when a we get more excited about 3rd party gear more than Canon.I disagree; the more options the better. I own a Tokina super-wide, a Sigma kit lens, and the rest of my lenses are Canon. Other than brand loyalty, what does it matter who is making the best lens?
Imagine if Sigma was still the old Sigma, and Tamron was the old Tamron...you'd have poor AF lenses that break, weak warranties, and you'd basically only have expensive Canon gear as your option. You'd be stuck waiting for the Xmas rebates to get reasonable prices. Instead, the used market for gear has gotten much cheaper, and Canon has been forced to cut their prices a lot after release.
I also think people forget, all the lenses that Canon has released in the last 2-3 years have been almost universally praised. The 70-200 and 24-70 are the holy grail for most pros. The non-L IS primes are really sharp (and now reasonably priced). Even the 40mm pancake was good, if a little odd. Even their kit lenses keep getting better. They just have such a successful line that they arent forced to swing for the fences like Sigma/Tamron are