As others have said, this is a frequently asked and answered question.
Ruggedness is not an issue for a begineer's camera, you should not be throwing it around.
Canon and Nikon have far larger lens systems. However, I'm not convinced that this is a critical distinction for a beginner. You will want to have choices, and you won't want to stay with the "kit lens" very long, but all of the major brands have more than enough variety to handle your needs until you become at least a serious enthusiast -- at which time you will know what you want and why.
Megapixels are pure marketing argument. For a beginner, all camera bodies have more than enough megapixels. There are downsides to having too many megapixels, but there are many questions here that address those issues, and beginners don't need to worry about them.
What do you mean by "discontinued"? There is no reason to worry about a model that has been replaced, say the Canon T4i compared to the T5i. There is a reason to be concerned about an abandoned brand, say Minolta, which is no longer in the market. But even for Minolta, they were bought by Sony and you can still get accessories and repairs. Realistically, begineer's cameras don't get repaired. They cost only about $500 and the minimum repair charge is well over $100, so if they break after you've had one a few years, you just buy a better camera anyway.
Recommendation: go to a real camera store, try some starter DSLRs and see which fit your hands. Buy what you like, buy it there. Do not go to a store and then buy over the Internet -- I consider that immoral in that you are wasting the store's personel's time.
There is a reason that most folks start with a Nikon or Canon "consumer" camera, its a safe choice.