Canon’s 15-megapixel EOS 50D with a maximum ISO of 12800 is a good candidate to compete with the Nikon D90, they are both great for experts but Canon is bit more expensive, so I would say "for the same price buy the cheapest" ;)

Its not a SLR, but it is a Canon.

I purchased a Canon PowerShot A480 10MP Camera for my Mum and dad. I played around with it for a few hours its amazing, easy to use and quick. 10/10 for the price of £60

So Canon gets a thumbs up from me! 

Canon and Nikon are like Coca and Pepsi, Mac and Windows, Boeing and Airbus ... you get my drift! Both are equally good, their pricing and feature lists are carbon copies of each other, and each brand's aficionado will tell you that their favorite is the best ever and leagues above the competitor!

Buy any camera that you like best and feel better with (check them in a store), but don't forget one thing: SLR photo it's like a computing platform, you don't buy a device, you buy into a system. If the chances are that you'll want to move up in the range and are in it for the long run, you're likely to stay with the same brand as swapping won't be easy. You need to factor that into your purchase decision.

As Roger mentioned above, at some point you will want to move up. I don't know this for Cannon (I am a Nikon user - D40) but for Nikon (most of) the extras you buy for one model (external flash, lenses, filters, etc.) will fit to all models in the range. This means that when you want to get a more professional camera you just need a new "body". 

From my personal experience, as a casual photographer (or even semi-pro) the entry models will do a great job for you!

I agree with Roger and Mircea..

Once you start with a system, you will be staying with it.

I am a Nikon SLR user for over 30 years now.. I have several Nikon objectives and Bodies.. For me to change to Canon does not make sense anymore.

Besides; as Nikon was the Nr. 1 Profi camera maker. Nikon started to make profi cameras in the year 1917. Canon was not even existing at this time.. Canon was a popular printer and copy machine maker in the 80-90´s..

Both Canon and Nikon companies are good friends in Japan. They know each other´s development levels and produce almost the same technology. They share the Worldwide profi camera market.

My conclusion: It is the matter of the taste.. Some like Nikon and the others like Canon..   And some others have the both systems..