It's way too early to tell.
Suppose Stafford plays four more years and averages 4000 yards and 25 TD over that span. Then he retires ahead of Marino in both categories. Six seasons at that rate and he passes Favre in yards. I understand that volume stats mean less and less over time, but there's a point where they can't be ignored.
Similarly, one can argue that the Stafford trade pushed the Rams over the top. If they should go another 3 - 4 years of deep playoff runs, his case begins to look much stronger.
Of course this is all purely hypothetical. If Stafford retired today, I would say it's a solid "no", but the book is not closed yet. I would put him in similar standing to Eli or Rivers, maybe a little ahead of Ryan.