Facts are pesky things. You might want to look into them. Iowa has nominated the last five Dem candidates in a row, and has only one "miss" since '96 - in '08, they chose Huckabee, as you noted. In '12, Mitt tied Santorum, 25 pct each. That's not exactly a "miss". In '00, they nominated W. In '04, W was unopposed. So, Iowa is 8 for 9 by my count. Nice try though.
Subtracting out the Democrats you had to run to in order to prop up your point, because what the hell that has to do with the GOP nomination, you are left with George W. Bush as the only GOP non sitting president to win the Iowa caucus since at least 1976, and then the nomination.
SO NO, they dont pick GOP nominees. They pick whomever can do the best televangelist impression.
Facts are pesky things.
That means Iowa has missed the last two in a row.
The trend is your friend.
Or not.....