I disagree. In general I think that once the principles involved are fully understood, writing from scratch a program that performs the same generic tasks as the human brain would be easier than emulating a specific human brain.

In fact I suspect that the code for an AI itself, if one is ever created, will be remarkably compact -- possibly the kind of thing that could be knocked up in a few lines of Perl once someone has the correct insights into the remaining problems. AIXI, for example, would be a trivially short program to write, if one had the computing power necessary to make it workable (which is not going to happen, obviously).

My view (and it is mostly a hunch) is that implementing generic intelligence will be a much, much easier task than implementing a copy of a specific intelligence that runs on different hardware, in much the same way that if you're writing a computer racing game it's much easier to create an implementation of a car that has only the properties needed for the game than it would be to emulate an entire existing car down to the level of the emissions coming out of the exhaust pipe and a model of the screwed up McDonald's wrapper under the seat. The latter would be 'easy' in the sense of just copying what was there rather than creating something from basic principles, but I doubt it's something that would be easier to do in practice.