Technically, NLHE allows for the largest edge of these three games. Equities run closer in PLO, and bet sizing in LHE prevents opponents from making catastrophic mistakes. Look at it this way: if a skilled player were trying to lose his money as fast as possible, which game would he pick? NLHE, because he could just constantly shove junk and get his whole stack in as a huge dog. In LHE, it's impossible to torch as many chips in a single hand, and in PLO, it's harder to be quite as big a dog.
If the question were: "In which game does the skilled player have the largest advantage in today's game conditions?" It's probably PLO, since there are so many attractive mistakes for the unskilled player to make.