That's a distorted view that you get from imagining if you had invested at the low of the last recession. Look at Japan's index, where it still hasn't caught up to the 1989 peak.
Calling a low is almost as impossible as calling a high. Though there are methodologies like Graham's which provide decent net-nets to invest in. A study on the Graham stocks since 1990: http://www.netnethunter.com/benjamin-graham-is-this-where-mo...
So, it really depends on the methods used to find the bargain which matters.