Very few stocks can be expected to build a million-dollar nest egg over several decades -- but Alphabet just might fit the bill.Online services giant Alphabet (GOOG 0.72%) (GOOGL 0.83%) has made plenty of millionaires over the years. You'd have more than a million dollars in the Google parent's stock today if you invested just $15,000 when it entered the public stock market in 2004. If you put the same cash to work in a broad market tracker like the SPDR S&P 500 ETF Trust (SPY 0.66%) instead, you'd have a t ...