I don't know why Ted Cruz is not considered around here. Of the Republican contenders, he is quite easily the smartest, most talented candidate in the field. Facing him would be a lot tougher than taking on Rand Paul the gaffe machine or Rubio the moron.
Cruz could be strong. A Harvard educated Hispanic man 20+ years younger than Hillary Clinton isn't necessarily the opponent she wants to have in a change election.
One problem with Cruz is that it's not clear if he's shameless and pandering to the base, or a true believer. A true believer is much easier to run against due to their increased willingness to say unpopular things, and the stronger likelihood of blind spots. A shameless liar can pretend to be whatever 50+% of the voters want. He would still have the problem that he's pissed off some prominent Republicans, which could lead to painful endorsements for Hillary.
I do think Hillary's strengths are overrated on this board. My take is that she'll be a weaker candidate in 2016 than Obama in 2012, as she'll be running for a third term for Democrats (candidates running for a third term for their party have done worse than candidates running for a second term since FDR) and is less politically talented.