Stack Exchange works, in part, based on the idea of crowdsourcing: you ask a question of a large, diverse population that provides you with a number of individual answers, and ostensibly the responses will converge on an answer that solves the problem you have.
To that end, it's essential Stack Exchange provides the opportunity for (mostly) anyone to answer a question at any time: there's no way to know beforehand whether the first answer is correct or whether some guy, 4 years from now, just happens upon the question and provides the best answer ever.
The end result is that questions will generally have multiple answers: that's good for everyone, as bad or non-optimal answers get replaced with better ones over time. The community converges on the best possible answer by voting: the answers the community and the asker generally consider to be correct right now will be at the top.1
If you're in a hurry or confused and did nothing but look at the top answer you're very likely going to be fine. If the top answer is wrong or doesn't help, that's what the other answers are for: if they didn't exist, there'd be no alternative to an answer that's wrong but happened to get there first.
There may be some merit to making the top answer more prominent, but it's already pretty prominent by virtue of being first (and very likely above the fold).
Note 1: unless the question asker accepts his or her own answer, due to conflict of interest