By Dan Weil The S&P; 500, which is dominated by mega-cap stocks, has dropped 17% this year. But there may be opportunities. The S&P 500, which is dominated by mega-cap stocks, has dropped 17% so far this year. While it’s only natural for investors to be freaked out by the move, there may be some buying opportunities amid the carnage. Morningstar lists five “market leaders” among the market’s 10 biggest stocks, as measured by market capitalization. Meta Platforms FBMorningstar analyst Ali Mogharabi puts fair value at $384, compared to a recent quote of $193.80. “While Meta continues to focus on…