LEGO Star Wars
I know what you're thinking, why is LEGO Star Wars on a list of classic games that essentially made Star Wars great for nearly ever major genre? Simple - LEGO bricks! Every kid loves LEGO bricks right? Why not combine them with Star Wars and introduce an entirely new generation of kids into the series? I can attest from first hand experience with my kids, LEGO Star Wars had a profound impact on how much interest a child had for the series. It wasn't until after they played this game that they thought anything about Star Wars, even after mentioning that it had space battles and light sabers. Once they played it in a child friendly setting, they wanted more.
Aside from the fact that it's just a damned fun game to play (sometimes frustrating!), especially if you have kids, the amount that it helped bring interest to a new series merits it being here.