The courier services provider needs to overcome some formidable challenges.UPS (UPS -1.01%), one of the world's top shipping couriers, hasn't generated millionaire-making gains since its public debut on Nov. 10, 1999, at $50 per share. It trades at about$85 today, so a $10,000 investment in its IPO would have grown to roughly$17,000. The same investment in an S&P 500 index fund would be worth more than $48,000.UPS underperformed the market as competition, macro challenges, and labor issues throttled its g ...