'Terminator Salvation' (Warner Bros.)Let's face it: without villains, heroes are boring. Without conflict, heroes sit around all day in their pajamas, drinking coffee, watching daytime TV, and waiting for someone to rescue. But enter an arch-enemy and wham!! Now the hero has a reason to get dressed and be valiant and virtuous. When it comes to science fiction movies, "a good old-fashioned baddie can transform even the most average science fiction movie into something quite special," says HecklerSpray, by way of introducing their list of the "Top 20 Sci-Fi Movie Villains."

Some good suspects are included: Jabba the Hut , the Alien Queen (Aliens), Agent Smith (The Matrix), and both Arnold Schwarzenegger as the T-800 in The Terminator and Robert Patrick as the T-1000 in Terminator 2: Judgment Day. (Check out the entire list at their site.) Naturally, that made me think of Terminator Salvation and its villain ... and then I realized I had no idea who the villain will be in McG's movie. We know Christian Bale as John Connor is good, we're not sure about Sam Worthington as Marcus Wright, and we know the mechanical monsters are bad -- but can a computer-generated creature really pull off the role of a villain?

Likewise, Michael Bay's Transformers: Revenge of the Fallen appears content to have its giant mechanical warriors once again serve as the villains of the piece. Looking over the summer release schedule, the only traditional villain I see is John Travolta as a train robber in The Taking of Pelham 1 2 3, but he could easily be overshadowed by Denzel Washington as the hero. Will CGI robots, rather than flesh and blood humans, really prove to be summer's top villains?