Prof. Mohanty writes on his blog that the focus on research is the reason why US Bschools are at the top of their genre. This "publish or perish" mentality is however, often at the cost of quality teaching time. Adding to that - profs as i see fall into 3 basic categories: 1) those who have awesome knowledge but are shoddy teachers (the kinds who keep bowling bouncers well above the head :P and never come down to those of us mere mortals), 2) those who are wonderful teachers but somehow their breadth of knowledge is limited and 3) best of both worlds - very good teachers and very knowledgeable too.
The first variety are, as they say, "dime a dozen". The second, not so many, but the membership to this category depends on perceptions (mostly decided on how well they are able to stand up to questioning etc.). Third, the real gems, are very rare to find. Feynman, i believe used to be one.
The problem lies in 2 aspects - teaching is a totally different job altogether from research. Teaching does not require immense knowledge - it only requires the ability to bend down to the level of those who do not know and the ability to lead them in the right path - in that sense it is a more people-skills thingy. Research, on the other hand, is more about stretching the boundries of knowledge - in that sense its more a mind-power/effort game. Feynman kind of guys fall into a category of people who amazingly seem to have obtained the right balance of both.