Why should they even have to look similar to the original actor? That original casting was done when they picked a 12 year old boy that they thought looked like Harry from the books and then grew up to be 5'5". Should they have to maintain his height? His eye color? His hair color?
The movie's casting was an interpretation, just like every other casting is. Asking that casting caters towards the original you grew up with is just saying "Always remind me of my own childhood, please."
Honest to god the fact that Daniel Radcliffe is a short dude makes me feel so good about also being a tiny man.
Completely unrelated to people gettin' huffy but seriously.