Kershaw is like Ford, while Benchmade and Spyderco are like Ferrari and Porsche.
Are there a few Fords that will eat any Ferrari or Porsche around a race track? Yup. But in general, the Ferrari and Porsche names are more respected because in general their cars are higher performance while Ford appeals more to people that want to spend less and care less about performance. When Ford wants to make a Ferrari or Porsche killer, however, they can. But Ford is more appealing to the masses while Ferrari and Porsche tend to make more models for performance junkies. On this forum, there are many knife performance junkies. However, we still love the high performance Kershaw models as they can be every bit as good as BM or Spyderco.
I love Kershaw, but brands can never be exactly equal. One will always produce more quality products than other, or do so more consistantly. Which brand is better is a matter of opinion. And in the general opinion of this forum, BM and Spyderco are the top 2 production knife makers. Not every brand can be first.
Kershaw makes a lot of great knives, some of which are every bit as good as top Spyderco and Benchmade knives. But in general, Kershaw is a rung or two lower on the ladder than Spydie and BM. Spydie and BM have more high-end models, and tend to use better steel at a given pricepoint.
For example, I love my Kershaw Leek. I think it is a better overall knife than my Native, and has a better design than any Spyderco or BM within the pricerange. But The Leek uses 440A steel. Spyderco and BM rarely use a steel this "low" in one of their popular and respected mid-level knives. They do use lower-end steel sometimes, but not nearly as often as Kershaw. Also, while the higher-end Kershaw models are great (Spec Bump, Nakamura), many feel the Manix, Military, Skirmish, 710, and even the Rittergrip are a little better.
Some people may prefer Kershaw to Spyderco and BM, as it's just a matter of opinion. But in general, knife fans on this forum will prefer BM and Spyderco. That is why you will see them prefered here more often. But I doubt many people here don't agree that Kershaw makes some first rate stuff. Many Kershaw models are very beloved and highly recommended here.
And remember that whether a company is first rate or second rate is very subjective.