Anyways, SpaceX is a huge endeavour as is Tesla motors and green energy project on the side. Most remarkable thing is a close loop those companies feed on each others achievements. That is without dispute. However, there is absolutely no widespread impact from all of this yet apart from PR waves. What it could be, and hopefully will be, is that either those group of companies have a widespread reach or (even more hopefully) those PR waves will incite similar movements across those industries it touches.
As for one of the greatest entrepreneur ever - competition is strong and large. While successful and visionary, his efforts are yet to come to full fruition where he might be among the greats. So far, it's all great business and great prospect. It could land among greatest entrepreneurs ever when/if those companies approach widespread impact of the likes of Ford, Dow, Siemens, Bell, etc...