And I'm sure because you played high school football it's comparable to what practice is like at an NFL level. Training camp and practice holds huge value in all professional sports, and it's how most coaches decide if a player is ready or not.
It's more than just practice too. Vick had plenty of time to run, lift weights, read the playbook, and prepare himself for the NFL. Not to mention he decided to stop being lazy and actually find some work ethic by his own admission. My guess is his new found work ethic had more to do with his success than anything else.
I'm not saying what he's done isn't very impressive, but compared to somebody coming off a serious injury who has to not only battle time off from the injury but the pain, setbacks, and limitations that come from an injury are just as difficult, if not more so than not playing football for 18 months.