I have a SLR camera and I wanted to know who makes the better lens?

I was looking to buy some lenses for my camera and I wanted to know which brand lens I should buy. I searched for Canon, Sigma, and Quantaray. I noticed Canon lenses are a lot more expensive. Which ever one you choose, what is wrong with the other ones. i.e. if you pick Canon, then tell me what is wrong with Sigma and Quantaray.

Are Nikkor lenses better than Canon and are they only for Nikon?

I like Canon lenses. You're paying for quality. Third party lenses (Sigma, Quantaray, Tamron, etc.) are cheaply made and don't always offer full compatibility with your camera.

Nikkor lenses have a great reputation as well. They only fit Nikon (I'm sure someone out there has a converter but it's not really worth it).

If you're on a budget and truly can't afford Canon or Nikkor, get an off brand until you can save up the $$$ for the real deal.

Actually, Nikkor makes the best lenses. The reason Canon lenses are more expensive than Sigma and Quantaray is because Canon has much higher standards when it comes to lenses in terms of composition (better glass), abberations (imperfections that may affect the image), etc. If you use your camera mostly for everyday photography like vacations, family, etc., Sigma or Quantaray lenses are fine. But if you're moving toward more serious "artistic" photography like nature or night photography, spend the extra money on Canon or Nikkor lenses.

It really depends what you are looking for in the lens. Canon makes great lens that are constructed really well. The top of their line is the L series and they get really expensive. Canon incorporates Image Stability in it newer L lens, and it really helps keep blur down in photos. Sigma also makes good lens, and they are generally a bit cheaper than the canons, but are just as good in most cases. Make sure, I'm assuming that you have a canon SLR or dSLR, that you choose a brand of lens that will fit your camera, because a canon lens won't fit a nikon.