I obviously love McNabb as an SU fan.
His numbers [to this point in his career, which is still being written] are borderline / right on the cusp, but I feel like he lacks a defining measurable like a SB championship. He epitomizes the good-not-great argument, although I strongly believe that for a time in his career, he was one of the top 4-5 QBs in the league for an extended period.
I also think that last year's debacle in Washington won't necessarily hold him back from HOF contention, but I believe that getting past that blip on his otherwise impressive career necessitates him bouncing back and having a strong couple of final years, building upon the aforementioned numbers. Would have loved for him to have 2-3 really solid years with the Vikings [or whoever] to close out his career, leading them to the playoffs, etc.
One other thing that has nothing to do with any of the opinions expressed above--for whatever reason, McNabb has been a huge lightning rod for controversy throughout his professional career. I've never understood why, because you won't find a classier guy who is less deserving of the negative attention. But in any event, there have been several dust ups in his career that have brought negative attention to him [the injuries, puking in the superbowl, the TO idiocy, the Rush Limbaugh attack, being traded, the Shanahan benching, etc.], and I'm sure that his eventual candidacy for the HOF will be equally controversial.