The Savings Bond Advisor has an updated performance comparison
between Series I Savings Bonds and the stock market (Vanguard S&P 500 Index Fund). This compares the two investments based on equal monthly contributions starting when the I Bond program began in September 1998. The black line shows the principal which increases in a straight line for each monthly contribution.
The red stock market line was gaining ground this year and it appeared it was on the verge of passing the blue I Bond line. You can see how the red line started to fall in the last few months. The graph stopped before the recent market plunge. So I think it's safe to say the I Bond lead will continue through this year.
Of course this doesn't prove that I Bonds are better than stocks. Here's what Savings Bond Advisor says
At any rate, no matter what this graph says, don't buy Savings Bonds expecting to outperform stocks.
Buy Savings Bonds because you can't get back less than you put in. They make a great foundational choice for the low-risk portion of your investment portfolio.
In my opinion, it also shows that even the long-term performance of a diversified stock portfolio is no sure thing.