There's more fiction than fact when people make this comparsion.

Like most financial discussions we've been having here comparing the S&P index fund to real estate investing is driven by the options of the people involved.
The source of most of this stems from the fact of every YouTuber out there touting real estate as the fastest, simplest, no-risk approach to nearly instant riches. 
Many of these "experts" aren't really trying to help you with sound advice as they are trying to sell their method of get rich quick. 
They all view real estate investing as the easiest way to wealth.
In reality, it's one of the hardest.

Not only is it the more difficult path it grows far more slowly than stocks.
One well respected financial personality noted that over the last fifty years the return for stocks have consistently hovered at about 12%.
 Again thats a fifty-year stretch.
Real estate however has given the average investor a 5.5% return over the same period. 
So not close.
If we had to end all discussion here a 12% return VS a 5.5% return would be more than enough to end it.

But we have to take in all the factors involved. Not just the easy ones. 
Theres a host of other reasons an index fund such as the S&P 500 is just the superior a product of the two.
Again the returns are as one-sided as can be. The S&P 500 returns about twice what real estate has. 
And it's been the case for over half a century.
For starters, investing in real estate, by definition, involves tenants. Most tenants, or even potential tenants I've ever had to deal with were to be fair, honest and decent. 
Needless to say thats not always the case. Most tenants will prove themselves just fine.
But one bad one is an ordeal.
 It's best to know how your going to handle the situations you WILL encounter before they happen.
Consistently late on rent, unrealistic expectations on the tenants part, damage on the tenants part. 
I'll stop here because the total number of issues could literally fill a book.
 Investing in real estate and being a landlord can be very profitable, despite all its inherent issues.

Another reason to consider the S and P, as opposed to real estate. Is it's liquidity. 
It could take months to liquidate your real estate holdings if you find yourself in some unforeseen financial bind. 
With your S and P however the process is instant. Contact your brokerage firm and have any amount of your index fund sent to your bank. Less than a day later it's there.
If all these reasons aren't enough consider this.

Not all real estate goes up.
 Some neighborhoods do go into decline over time for any number of reasons.
Should you find yourself as the owner of a rental property in such an area you've now got TWO BIG PROBLEMS.
First, the rental price you can reasonably expect is greatly reduced and of course the client class you will now be dealing with might not be as financially stable.
By the time you decide to sell the rental in question you will find you'll be getting less money than you originally believed you would, and almost certainly having a more difficult time when selling it.

So yes, you can get wealthy, even rich over time with real estate. 
But it's not as fast tract to wealth.