wild horses are the same until their spirit is broken n they're tame...a rideable dragon sounds like a respectable mount for a dragonborn, who better then a dragonborn to tame a dragon? he speaks some dragon so all he has to do is shout dragon,whoaa!

I think you missed a few points there. Dragons are intelligent. When was the last time you sat down to discuss the finer points of philosophy with your horse? "Taming" a Skyrim Dragon to the point that it would allow you to ride it wouldn't be animal taming and training, it would be slavery. It would know who you are, what you are doing, who it was, and the fact that you are enslaving it.
That is one of the biggest reasons to not allow users to 'tame' the dragons.
Now, if there was a group of dragons who wished to preserve the freedoms of the "Lesser small mortals", and allow them to live apart and of their own free will, and one of them wished to carry you for its own reasons, then that would be different. (If this is already in the storyline, shut up about it! We don't need/want to hear confirmed spoilers.)