Having seen all of Jacoby's games with us and a few of Jimmy G's, its easy to spot the talent difference. I have never seen Jacoby play out of his game manager role. He always did just enough to not be a liability. Imo, he has never shown to be able to take over a game when the running game or defense lays an egg. Ever. Jimmy G, last year after he was traded (haven't watched him this year) played really well. Even if his stats didn't show it, he played like a guy who can make all the throws and win despite the team around him not playing its best at times. That's why they awarded him a fat contract.
I honestly can't see Jacoby being more than a solid game manager.
Emmitt is the best RB of all-time, he played with one arm at NY with HFA on the line and dominated, won the game by himself basically. He is the all-time leading rusher and has more TD's than any other RB. He won 3 SB's too. To me that = best ever.