According to Cinematical.com,  Sylvester Stallone had commented on why certain action film stars weren't included in "The Expendables".  Two of the stars in question were Jean-Claude Van Damme and Steven Seagal.

Stallone was quoted as saying, "I wanted to set Jean-Claude against Jet Li, but he didn't want to lose to Jet. He didn't think that was cool. But that's why it would be cool; to have Jean-Claude beaten by the other man. Hey, they could have a rematch. But Steven Seagal and Van Damme, they weren't really into our gallows humor."

So, not only did these two actors supposedly let their egos get the best of them, but they missed out on being part of a number one film. Some say, however, that they were wise in not choosing to do the film, since it has gotten some criticism from action film fans.