Average ROI for different types of real estate

[JC Skweres]

Has anyone see average & median ROI for different real estate niches over longer periods of time (like 5, 10, 15, 20, 30 year)?

I'm trying to compare stock portfolio return to returns from different real estate niches to determine if I should focus my time on REI. I keyed in on the following article which seemed to imply that single family homes have less return than other options, but it didn't offer any specific numbers:
http://www.biggerpockets.com/real-estate-investing/strategies-niches
- Raw Land
- Single-Family Homes
- Duplex/Triplex/Quads
- Small Apartments
- Large Apartments
- Commercial
- Mobile Homes

Ideally it would be published by a 3rd party organization somewhere..

I've been digging through different articles / forum posts and maybe I'm search inept, but I can't find a nice table with everything together. I see people talking about infinite returns, but eventually you run out of time maintaining current properties and finding new opportunities so I see this as a false argument. Maybe the first 3 properties have a high return, but eventually it slows down and I'm interested in the longterm returns the average / median person achieves. I know there is turnover involved and generally the people I've observed who own property don't go beyond 3 properties (I have no idea if this is the rule or my limited experience).

You all have an incredible amount of knowledge so I appreciate any help you can give on helping expand my mind.

Thanks,
Jim