Which is the best Digital SLR camera . I would lay more stress on optical zoom and them Mega pixel .?

Which is a better choice Nikon or Canon ?

From resent research two cameras with 5 megapixel and 9 megapixel, has no difference. Someone did a study and took a picture with both cameras, enlarged both of them to the same size, and both pictures looked the same with the same amount of pixels so it doesnt really matter about megapixels once u reach a certain amount.

i would suggest using these websites to chose teh appropriate camera for your likings.
http://reviews.cnet.com/Digital_cameras/...
http://cameras.about.com/od/professional...

FYI Cnet is very good at reviewing and rating many different electronics so u can use that anytime for anything.

Photographers would say, it's not the equipment you use, but the eye of the person who uses it. In short, it's in how you take the pictures.

Nikon and Canon cameras each have their own strength and weaknesses, so it wouldn't really matter which one you get.

But to better aid you in your decision, you may want to check out http://www.dpreview.com and/or http://www.steves-digicams.com

they offer an in-depth review of the digital camera you're planning to buy. and DPReview even compares it with its same-level camera (i.e. Nikon D50 VS. Canon EOS 350D... etc.).

a lot of people use canon. and does not matter how much megapixel the camera has, as long as it is digital SLR...

Nikon and Canon are both up there. Its been a long standing debate who takes the cake. So you wont find a definite answer.

My suggestion is take either of them and you wont regret it ever.

As for the best digital SLR, I want to let you know that there is no fixed Optical Zoom associated with a camera body. The zoom comes from the lens which is a removable resource.
Consider browsing through the Canon/ Nikon catalogue or ebay listing to find the DSLR camera body in your range.
For the record I have a Canon EOS 300D and I am very happy with it.