Personally, I love all my Nikons, I've had 2 DSLRs, 2 point and shoots, and have given my girlfriend 2 nikons as gifts as well, I really have no reason to say that Nikon is better than Canon, I just know how to use them and I'm used to them and don't feel that the quality is worth me switching over and re-learning how the camera works. I have used my friends Canons and they are very nice, but I just don't know how to work them as easily. Again, this is personal opinion, but I really just don't see that much of a difference, yeah, some are better than others, but each have their own good models and bad models for what they do. I feel that Nikon is more user friendly and easier to handle, while Canon has slightly nicer quality and colors but are a bit harder (at least for me) to use well.
HOWEVER, I will ONLY use Canon for Manual SLR (not digital), because that's what I've always used and I love the picture quality I get from them.