[Snowflakian]

A good chunk of the reason they didn't do well over the film is quite simple.

The movie itself is a spectacle for 3D. Something visually stunning to experience.
This doesn't translate to toys. Toys need to be of memorable properties that kids want to experience over and over again. Not something for a visual spectacle like Avatar, that's really just a generic movie of smurfette's creation. For that matter really though, no movie only original lines tend to survive. Look at ID4, and the plenthora of brand new IP lines that have had no staying power for this reason. As opposed to something like star wars that didn't need an effects extravaganza to sell itself. Star wars has stuck around because of the characters themselves being memorable and everlasting.