Empirically, a retail investor will realize the best return by investing in an index fund. In fact, the more you trade, the more likely you are to lose money.
I would agree with you 99% of the time. Most retail investors have no knowledge of the market (especially ones i talk too)and end up buying a bunch of crap (i.e., RIM, Sunpower, Facebook, Nokia...etc) because they are "cheap" or they like the product (meanwhile 99% of population hates it) or it is the current hot stock. Instead they shart their pants when 2 weeks later the stock takes a nosedown after it is downgraded/they report bad earnings/financial meltdown a la 2008.
I've been trading individual stocks (and options) with real money for about 7 years now ever since i turned 18. After making back losses from the 08 crisis i am up about 30% on a money-weighted return. I invest usually in what i know, i.e. tech stocks.
Sixty percent of the time, it works every time.