Agreed. Basically there are no discrete events in the other major US sports.
Offense isn't any more concrete...too many variables like o-line play, QB versatility,etc. It's not as simple as pitcher versus batter and field variances. I agree. And this is why I'm not a fan of fantasy football. It seems to disrespect the team concept of the game by making it about individual players and disregarding the importance of line play, play calling, etc.
It's all about the line. While certain backs are talented enough to produce big numbers with sub-par lines in front of them, the majority only excel if the group in front of them are dominant. I don't think McGahee will ever put up consistently great numbers unless he runs behind a great line. Minnesota comes to mind. Running behind guys like Hutchinson, Birk, and McKinnie, Adrian Peterson or Chester Taylor look fantastic. I seriously doubt Peterson would have the huge stats he has if he was playing for Baltimore or Buffalo. In my opinion, Hutchinson is a key. He anchored a line that allowed Shaun Alexander to dominate in Seattle, and now that he's gone, their running game suffers. He goes to Minnesota, and Peterson runs crazy. When Cleveland passed on Peterson and drafted Joe Thomas instead, many Browns fans were upset. In the long run, though, I think they'll see they made a great decision. Bolster your line to the point it's dominant and you can find any number of backs who can be very successful. As a side note from a Bills fan, I would still like to thank Baltimore for taking McGahee. He's a malcontent and not half the runner Marshawn Lynch is now or will be in the future. Willis is custom-made for the horrible offense Billick has put together in Baltimore.