Pictionary includes a board game element with teams and some other folderol I think.. the core gameplay element, I.e. "I draw something, you guess what it is" has been around long before there was a Pictionary, or a Draw Something, or an Isketch, or InkLink, or ....

It would be like trying to sue someone for an implementation of tic tac toe. Though in today's environment, I'd be shocked to learn someone hasn't tried.