As you expand your time horizon out further and further, cash and CDs will lose you more and more and more money relative to stocks.
You guarantee a rate of loss equal to (inflation x time) with cash. Over the next 5 years, your cash and CD investments will lose somewhere between 3-10% value. Over, say, 30 years, you can plan on losing 80-90% of the principal's value. Sounds like a SHITTY investment to me. Cash should be used as a medium of exchange, not as an investment!!!
Conversely, your risk of loss gets lower and lower holding safe blue chips and index funds over a long period of time. Over the next 5 years we might see a recession that decreases value 50%. However, over 30 years the growth rate of the stocks(businesses) you own will negate any temporary volatility and you could see growth of 1,000-2,000%. Sounds like a GREAT investment to me.
If your time horizon is less than 10 years, hold a mix of cash and stocks that's 50/50. If there's a really bad recession you can buy more stocks with the cash you have to multiply your future earnings. Longer than that, mostly stocks. Blue chips & passive index funds would be ideal.