In terms of VBD, Manning is currently at 140, which is is best (his 2004 ended up at 129). Brady's 2007 was higher, at 180 VBD points, mostly because the #12 QB scores more now than they did in 2007. Marino's 1984 also happened to be 180 VBD points. Steve Young had 179 VBD points in 1998 (his last full season).
The big RB seasons are a lot bigger than that (in 2-RB leagues), because the #24 RB doesn't score very much. Tomlinson's 2006 was 266 VBD points; I think that's the biggest VBD season of all time. Priest did 218 and 231. Marshall had 208 and 222. TD had 233.
But I think the most impressive VBD feat ever was Rice's 215 in 1987, when he put up 215 VBD points in just 12 games. That means that Rice put up 18 points per game more than the #24 WR. (And 7.5 points per game more than the #2 WR).
O.J. Simpson had 282 VBD in 1975, which is the highest total I've ever found. And it came in 14 games; give him two more, and I think he easily could have topped 300 VBD. Which is absurd. O.J. Simpson had more VBD (282) than the #3 RB had TOTAL POINTS (264).
If we're talking about shorter seasons, like Rice's 1987, then Wes Chandler's 1982 is far and away the record holder. He put up 190 VBD...
in eight games. That would project out to 380 VBD over a full season, even discounting the fact that the baseline is skewed because most WRs played 9 games that year. His stats would pro-rate out to 98/2128/18 in a much less WR-friendly environment. The #5 receiver that year was Wesley Walker. If you pro-rate Walker's stats out to 16 games, he'd have had 69/1100/10.7.