Sorry it's taken so long to respond...
If you were to make an NFL league, creating all the rosters as accurately as possible (and that's no small feat), using Hack's playbooks (he's created the best 11-man playbooks out there), you would probably have a fair representation of the 2012 season, yes. Not an exact replica by any means, but the results, I would say would not be wildly dissimilar to how the year played out.
To give a very small example, I ran a Grey Cup simulation before the CFL Championship Games in 2007 and 2012 (PC issues prevented me from playing in the interim).
The 2007 Grey Cup simulation had the Saskatchewan Rough Riders defeating the Winnipeg Blue Bombers 22-19
Actual final score of the 2007 Grey Cup: Saskatchewan Rough Riders 23, Winnipeg Blue Bombers 19.
The 2012 Grey Cup simulation had the Toronto Argonauts defeating the Calgary Stampeders, 47-7.
Actual final score of the 2012 Grey Cup: Toronto Argonauts 35, Calgary Stampeders 22.
So, yes, if you can take the time to do the rosters, the game can do an accurate job of emulating the real life game. That said the time it took me to create and tweak the real rosters for eight CFL teams was six weeks. I can't imagine how long it would take to do thirty-two teams.
It's time to kick ass and chew bubblegum... and I'm all outta gum.