The vast majority of professional fund managers fail to beat the market, with super-computers, access to CEOs, and all the data on the planet at their disposal. To think that the little guy can beat the market consistently over time seems extremely unlikely.
It seems pointless to me to talk about "what if" you'd invested in Google, WM, Apple, Fed Ex, Microsoft, whatever. You'll never know more about one of these businesses than professional fund managers. If you made a mint on one of these, great, but there was a huge luck component, not something I want to rely on.
The market is skewed toward computer-powered manipulators. "High frequency" trading firms use super-fast processors and trading algorithms designed and tweaked by PhD's in real time every single day to rake tens of billions of dollars out of the pockets of average investors each year, through manipulation of bid/ask spreads and direct data pipes into the major exchanges. The exchanges look the other way because of all the revenue earned.
Hedge fund managers run equally complex processes, with armies of PhD's, lots of bribery-induced insider trading info, to also outmaneuver the little guys.
It just seems that real estate offers a much more level playing field for the smaller investor due to the sheer physicality of it, the need to see it, touch it, do accurate rehab estimates, etc. There are countless inefficiencies and supply/demand imbalances which can be exploited.
No doubt, as Jason said, there is money to be made investing your "private equity" into smal businesses that you have knowledge of (such as Joel mentioning buying a beaten-down restaurant franchise that will generate 60k of fairly passive cash flow). This is more like RE in many ways and unlike investing in publicly traded stocks.