If you like politics, then it's fun/interesting to watch the horse race in the Republican primary (the Democratic primary lacks the same drama and has played out as predicted so far). But, if recent history is any guide, I wouldn't give the current polls a lot of value if you're trying to figure out who the 2016 nominee is going to be.
Looking at the last four contested primaries, the eventual nominee hadn't moved to the top of the national polls until January or February.
In 2004, eventual Democratic nominee John Kerry was behind in the polls until late January, 2004 - several days after the Iowa primary.
In 2008 the polling was similar on the Republican side. Two months before the Iowa caucus, McCain was in third place, and with less than a month to go, he would drop to 5th. Here again, he wouldn't become the front runner until a week after Iowa, and 3 days after New Hampshire.
The 2008 Democratic primary polling looked somewhat similar to the way it looks this year, with Hillary Clinton sitting comfortably ahead of the field, but then at around this point (two months prior to the Iowa caucus) Obama began to move up steadily in the polls. He didn't become the front runner in National polls until mid February, nearly 6 weeks after Iowa.
And of course, much has been made about the difficulty Romney had in 2012 consolidating the support of Republicans. After leading for much of the early part of the campaign, Romney lost the lead 5 times between June 2011 and March 2012 to 4 different opponents. He did lock down a lead in the national polling until the last day of February, nearly two months after Iowa.
The 1992 Democratic primary was also late to develop. Back in 1992, Clinton didn't finally take the lead until early March (a few weeks after Iowa), and the person he was behind prior to that wasn't even in the race.
Of course, this is all in contrast to 2000 a year with no incumbent candidate and a year when both eventual nominees were front runners before they entered the race, and remained front runners to the end. Which is how the Democratic nomination is looking this year.
Similarly, in 1996 Dole led the Republican primary polling from early November, when he regained the lead from Colin Powell after Powell announced he would not run, until the end.