That doesn't mean real estate is a terrible investment. I've done pretty good so far with real estate. I also personally have no problems using ROI as my rate of return, because I'm not using other people's money to buy stocks or businesses; my borrowing potential right now wouldn't be utilized if I wasn't using it for property. But even if you're using the entire leveraged amount for your numbers, i'm sitting at 16.xx% on one flip (owned it a year), and my latest one (bought last may/june), if I sold today, would be sitting at about 15ish% on a conservative estimate of what i'd come out of it with.
I dont know enough about other investments to see similar 'obvious' increases like I have so far seen in real estate. Getting a mortgage on real estate is pretty easy to do too; any bank will do it and it takes an hour. So I like real estate so far. The problems with it can often be solved by trading your time rather than money also. That's good starting out doing it a hobby, maybe not so good when you have 20 properties and it becomes a full time job (just finding a renter for my wife's place I probably wasted a good 15 hours of my life).