Those claiming the housing market was in a bubble that would eventually come crashing down used the following two examples to demonstrate their point.
This is another graph, in blue is the median home price in the US in actual dollars. The red line is the same value only adjusted for inflation. The thin blue and thin red lines are what the poster believes is the normal trajectory of home prices which it follows very closely until 2000. The poster believes the prices still have a little bit farther to fall before they line up with their normal trajectory and can begin to increase modestly like the previously did before the bubble.