What command lines are extremely lacking in is not "intuitiveness". For anyone who is passably literate (or maybe even just anyone who can speak), using words to say what they want is quite intuitive (in the "familiar" sense, which seems to be what UI discussions fall back to as a working definition for "intuitive"). No, what command lines lack, in most (if not all) current implementations is discoverability to the vocabulary and grammar, some friendly feedback, the forgiving-ness that new users need to get past that fear of doing the wrong thing, and hand-holding teaching-the-steps-toward-complexity kinds of things (if complexity is wanted by the user).
Someone in another thread mentioned that their parents have trouble with even the abstraction of programs for tasks. The parents know what they want to have happen "send an email to their son", but connecting that to a program that needs to be started and used and then possibly closed again is something they seem to forget. Well, in that case, a simple command line environment for getting them to the right task-based interface would be as good as anything else, so long as it had a natural and discoverable vocabulary. It is perfectly natural for me to put some words in a row to communicate to you what they wanted, and at some point they probably put some words in a row to tell him what they were getting frustrated with the computer about. So why is it that one would think that having them put the same words in a row for the computer is somehow, despite being quite intuitive in all these other contexts, suddenly for the computer it is not intuitive?
No, back in the day computers simply weren't up to the task of interpreting all the myriad ways that someone might have said "email my son". And command line environments were not made with discoverablity, friendliness, and forgiveness in mind. The people using them were willing to bend their own minds to the limitations and peculiarities of the command lines. And instead of making them better and better for other users, the programmers and designers thought they could get more bang for the buck with pictures instead. Thus things have gone quite far down that path until we are arguing over what visual cues for controlling stacks of windows of disparate interface paradigms are more intuitive, what icon best reminds people of "email", and how to get them to notice/remember which text box they should put their son's name in. Meanwhile computers are quite powerful enough for someone to take an fresh, intelligent stab at merging a command line back onto the screen so that computers can finally catch up to taking commands the way a normal three year old finds perfectly intuitive.