Hey Kev....as LOBOREX said, you know who it is straight away....you already have a caricature piece right there....that is not a put down, but a compliment. If you have brought out the characteristics of a likeness that quickly, you stand a chance, with lots of practice and observation to sculpt a serious likeness. No one can expect to produce a perfect likeness straight off the bat.
The next time you have a go, find a front/face on shot, a left and right profile (if you can't find both, use one and just flip it in some editing software. Not ideal, but better than nothing) and finally a view of the back of the head. There are so many pics of people out there, you should be able to find someone that has had photos taken with these profiles. Ideally three quarter shots of left and right sides would be good. If you have editing software, attempt to place the images alongside each other and at the same scale. Decide the scale/size of your next sculpt and size the images to that chosen scale. You might think this is way too complicated, but if you stick to attempting to scale the images with the sculpt, you stand a better chance at improvement. What you need to do next is print off 2 sets of images, one to look at and copy and the next set to cut out. So taking the second print out, carefully cut the head out, but instead of saving the whole head, you need to keep the outline. This counts for the side profile and front face shots. You will be able to control your sculpt by offering the cut out to the sculpt as you go along. So each time you offer it to the sculpt, you will see where you have not added enough, or perhaps too much. Near perfection will allow you to slip the cut out onto the head, with the sculpt passing straight through. This is not cheating, but will allow you to get the profile right. The rest is observation and measuring. Placing an eye/s just 1mm out will alter the likeness. It really is very, very difficult to capture a likeness, so don't give up thinking you can't do it. What this method will do, is help you get nose, chin and forehead shape correct from side profiles and the correct width of head, jaw shape and ear set correct. You still need to observe all the other elements as well, but at least this should primarily help you or anyone else in making a good start.
Regardless of which method you choose, I look forward to seeing the next one. Whatever you do, leave Einstein alone. Put him to one side and don't attempt to improve him because you won't be able to. He needs to remind you that he started you off as a likeness sculptor.
Good luck
Ant