Jillian's has a lot going on. I think the main attraction is the arcade- it's filled with tons of games-even some you can ride. But for those that like to drink, Jillian's offers plenty of opportunity. From the downstairs bar to the upstairs nightclub, you can get smashed and then go out and race your friend on some motorcycle game or challenge each other in a rousing game of skee ball.
I recommend the nightclub. While there's usually no one in it, they have fantastic drink specials (when I went, they had $1 martinis) and the DJ will play anything you ask. Check it out!