I am not sure why you are comparing Nikon D60 and Canon EOS 450D, is it because both these are recently released?
Also check out Nikon D80, similar to EOS 450D price range. I would swear thats its the best camera in the world. but it has lens thread of Nikkor AF / F-mount, D-Type. (Wider range of lens one can use include cheaper Sigma type) Catch the dp rating
www.dpreview.com/reviews/compare
Canon EOS 450 seems to have higher image resolution. But like Magnus said its the lens that makes the difference.
Recently I had my hands on Nikon D300. We were doing a low light shooting. That camera blew-me-away. Off course High-end camera are expensive and people who buy them make a living out of it.