I watched those two fan-made trailers... and I have to say that of the two (John Cusack, and Ed Burns) I'd have to go with Burns.
Cusack definitely has the average-joe appearance, I just don't think he's got the ability to portray the rage that Jack struggles with.
Personally, when I read the books (or should I say reread them) I tend to try to find an actor that would fit the role. Not an easy task. Some actors have some qualities, but very few have all of them.
Those actors that jump to the top of the list (for me anyway) are as follows:
Jason Stratham (of Transporter and Snatch fame). The only real hurdles I think he would have to deal with in the role of Jack would be his accent, and... well, his hair. I don't think anyone imagines Jack with a receeding hairline. However I think the character Turkish from Snatch would really fit the aspect of 'Jack' where he's trying to blend into the crowd, while the character he played in Transporter would be the aspect of 'Jack' where he's forced to get physical.
Mark Walberg (Italian Job, Planet of the Apes)... Yeah, I know. But he is a pretty good actor and has the physical makeup necessary for the role, as well as the ability to conceal that. He also fits more in my mind as the right age for Jack.
Keanu Reeves... just kidding. hehe...
Matt Damon (Borne Identity) Actually, before seeing him in that role I wouldn't have considered him for a potential Jack. After seeing it, regardless of the fact that they really mangled the novel, I can't deny that he might make a good Jack... although I see Jack as being a bit taller but hell they can make anyone look any height in movies these days.
To me, Cusack is too average.. and Burns is too good looking. I also have a problem with Burns acting ability, but that may just be my problem.