I agree that Tesla was a great man and the greatest genius the world has ever seen, and only history will tell whether Elon Musk's legacy will be anywhere close. But you underestimate Musk massively if you assume that he isn't trying to do anything for the betterment of mankind. His 3 main recent projects, Solar City, SpaceX and Tesla (including power storage modules) are all his attempts to deal with climate change. The way he presents it (and I don't think he either a good liar or a good actor), he worries for mankind, and is using his tech and business skills to help mankind deal with this issue, with SpaceX being the insurance policy in case all is lost, and humankind needs to colonise another planet. He talks about becoming a "two planet species", and if we risk being erased by an errant asteroid, that might be a good insurance policy.
Tesla, for all his genius, wasn't so great at actually getting his work into the hands of people - perhaps he lacked people and business skills. That's why Edison gets the credit he does, even though he by many accounts was, well, a bit of an ass.