You want a real choice? This explains it.
From the article:
But some of the main obstacles that third parties face are artificial, not structural. "The two old parties have gamed the system," Johnson charges. The Presidential Debates Commission, or CPD, the private group that serves as the gatekeeper for the nationally televised debates, imposes an arbitrary barrier of 15 percent support in three national polls before a candidate can be included. That rule, adopted in 2000, would have barred virtually every third-party candidate in American history. The fix is in, it seems.
The article also states that Gary Johnson is the only candidate that does not support the Patriot Act and does not want to bomb Iran. I would add that Gary Johnson is the only candidate that does not support the indefinite detention of American citizens provision in the NDAA.
Johnson also states from the article, when asked about his candidacy guaranteeing an Obama win, "He says he gets that a lot: "The implication of the question is that I'm gonna take votes away from all those ... anti-war, pro-gay marriage Republicans that are currently supporting Romney." Johnson admits that his candidacy hurts Romney in North Carolina, but insists, "I take more votes from Obama in New Mexico."
I can't fathom why he is "unelectable".