Wes, I have done some Aiki-jutsu, and I would say it is very different from aikido. It depends what you mean by invent. Although the 'techniques' are similar, the feeling of doing many of the techniques and the principles are different. Also, didn't Ueshiba 'invent' irimi-nage?
It is always difficult to compare any martial arts or styles because there are inevitable similarities as well as differences. You will see the same in other martial arts (there are many styles of karate - although these seem more formalised and they are less likely to train together than they would in aikido).
Aikido is different from many martial arts to the beginner because it is more about perfecting technqiue rather than learning new ones (learning the techniques is relatively quick compared to being able to do them effectively). Also, the fact that in aikido we have to blend with an opponent (rather than doing set kata) makes aikido very personal to the individual. Each Nage and Uke has their strengths and weaknesses. As you train you use what works for you; but this will mean you will also teach what works for you.