How well do the best Pentax lenses for DSLR rate compared to those from Nikon or Canon?

I need to upgrade my camera and lens system. I am going to get rid of my Olympus E-510, and upgrade to something like a Pentax K-5 II, Nikon 7000, or Canon 7D. From what I have heard about the Pentax K-5, I think I like it best, but am unsure how well the Pentax lenses compare to the Nikon or Canon lenses.

Budget constraints prevent me from going to a full frame sensor camera, but I can build a pretty decent ASP-C based camera system over time.

I am willing to slowly build up a set of premium prime lenses, but will start with a normal range zoom lens for its versatility. Whose lenses stand up the best, and which manufacturer offers the best performance for the money?

Kendra