Yes, polls mean nothing before the conventions, in terms of predicting the final result. Dukakis led Bush by 17 in July 1988, Bush led Gore by about 20 in January 2000, Carter led Reagan by 30 points in January 1980 and still maintained a substaintial lead even into June, Clinton was running 20 points behind Bush in January 1992 and in 3rd place, and was still running 3rd as late as June, Carter was 30 points ahead of Ford in summer 1976. Mondale was never ahead of Reagan in calendar year 1984 though, at least not in the Gallup poll. Maybe in a different poll he was.
Unfortunately you had a very weak recovery in 1992 with unemployment still rising, it was near 8% by the end of 1992. The rise in unemployment and weak GDP numbers hurt Bush as the impact of the recession sunk in more. Also, 1992 was riddled with high crime rates; crime peaked in '92 and '93 after a 8-year upward cycle. Right now crime is a much smaller issue. The atmosphere in '92 was very humble and self-depreciating for Americans. We were losing to the Germans and the Japanese; we were the world's biggest debtor, we had tons of social problems, Paul Kennedy's prediction about the "decline and fall" was coming true. This year the mood is different-- while most Americans still think the country is heading in the wrong direction, its less pervasive than it was 12 years ago.
Also, January 1980 was the peak of an economic cycle and Carter's high approval was affected by the Iran hostage crisis which had just started 2 months earlier. The year ended up being a recession year with high inflation, which is something that is unlikely to happen this year. And of course there is no hostage crisis to throw things off.
In '84 the economy was still recovering from the worst Post-WW2 recession in US history, for many people the worst economic times they had ever seen in their lives. Unemployment stayed at nearly 10% even up to late 1983, that may explain Reagan's poor polling. But the turnaround was quite apparent by late 1984.
