But there's a small problem that might bother some investors. The average price-to-earnings ratio and price-to-book value ratio of Vanguard S&P 500 ETF are 27.7 and 4.9, respectively. For Vanguard S&P 500 Growth ETF, those figures are 34.6 and 9.4, respectively. The growth-focused version of the S&P 500 is looking really expensive right now.

Vanguard exchange-traded funds (ETFs) are a fantastic choice for retired investors looking to play the long game with their portfolios. Undoubtedly, Vanguard is a name that passive investors can put their trust in.

Here are my three favorite Vanguard ETFs to buy and hold for decades. Warren Buffett doesn't give a seal of approval to ETFs like Good Housekeeping does with consumer products. If he did, though, I suspect the Vanguard S&P 500 ETF (NYSEMKT: VOO) would be the first to receive such a distinction from the legendary investor.

The Vanguard Growth ETF and Vanguard Value ETF are two simple yet effective ways to invest in small pieces of hundreds of large-cap stocks. But the Vanguard Growth ETF has become less diversified in recent years, whereas the Vanguard Value ETF is still very diversified, even with its focus on financials, industrials, and healthcare.