Riffing off of Grad's post regarding QB and RB talent, let's take a look at talent versus season results:
2002: Krenzel, Clarett - 14-0 BCS Champions, Big Ten Champions
2003: Krenzel, Ross - 11-2 Fiesta Bowl Winner, Big Ten Runner up, only scUM loss
2004: Zwick/Smith, Ross - 8-4 Alamo Bowl Winner
2005: Smith, Pittman - 10-2 Fiesta Bowl Winner, Big Ten Champions
2006: Smith, Pittman/Wells - 12-1 Lost BCS Title Game, Big Ten Champions
2007: Boeckman, Wells - 11-2 Lost BCS Title Game, Big Ten Champions
2008: Boeckman/Pryor, Wells - 10-3 Big Ten Champions
Note that the 2004 team put exactly two Seniors in the NFL via draft: Mike Nugent and Dustin "Safety" Fox.
As grad mentioned, you see two dominant RBs, plus a solid RB who was drafted in the fourth round (Pittman). The best seasons tend to correspond to having a combination of a good or great back (2002, 2005-2008), combined with stability and experience at QB. The two "worst" seasons since 2002 are the two seasons in which QBs were changed, and as the saying goes, if you have two QBs you don't have any.
Yet despite unheralded talent at QB, Tressel still was able to go to the BCS title game with Krenzel and Boeckman. Perhaps this shows that he's better at managing average talent and getting exceptional results than he is at managing exceptional talent. Even Troy Smith, while highly rated, was not nearly as hyped coming out of HS as any of the USC QBs. In fact, USCs transfers and backups were more highly rated. See John David Booty, Rocky Hinds, and current third stringer, Mitch Mustain.
Noting that Ohio, as discussed in one of the recruiting threads, has not exactly been a hotbed of QB prospects over the past decade, it's understandable that we've lacked USC's embarrassment of riches at that position. However, Tress seems to do just fine in keeping average QBs within their limits, and in developing them to their potential.
Tressel's offense is most productive when he has a talented RB, or better yet, a pair of talented RBs. Given the current depth chart and recent recruiting, that part of the talent equation is probably safe. Again, though -- looking at USC as an example, OSU has not had the quality and depth of backs the Trojans have, despite Beanie. Clarett played for merely one season, and we don't need to rehash Lydell "Passin' Bills" Ross.
I think the offense issues are overstated. When the pieces are in place, things click. The reality is, hyperbole, chest thumping and Buckeye Pride aside, OSU has most certainly not had the level of talent on offense that other major programs have, outside of the Smith-Ginn-Pittman era, which featured a highly productive offense. If anything, Tressel has gotten more production out of less than anyone in the country. I'd like to see Pete Carroll, Norm Chow, and the creature once known as "Sarkiffin" do more with the 2003 offense, for example.