There is no tried and true method in determining the best NFL players.
But pro-football-reference.com has one scientific option: Approximate Value.
Is this a perfect way to determine, say the best all-time draft picks for a certain team? Maybe, maybe not, but it seems like a decent way to go. There are flaws to this methodology, such it really begins in 1960 and perhaps you don't agree with the computations. For more on the Approximate Value you can read much more about it here.
For our purposes, we're going to use Weighted Career Approximate Value (described as "100% of the player's best season, plus 95% of his 2nd-best season, plus 90% of his 3rd-best season, plus 85% of his 4th-best season" and so on).
To determine the best draft picks in Minnesota Vikings history, we ordered it by the Approximate Value only for when that player appeared in a Vikings uniform. For example, Fran Tarkenton was drafted by Minnesota but also played for the New York Giants. You'll see in the chart below both Tarkenton's Career AV but also his Vikings AV. This also eliminates someone like Bobby Bell, who was selected by Minnesota in the second round of the 1963 NFL Draft and has the highest Career AV of any player ever draft by the Vikings but who chose to sign with the AFL's Kansas City Chiefs (and never played a down for Minnesota).
So, with that out of the way, here are the top draft picks in Vikings history, according to their time spent playing for Minnesota:
Perhaps not surprisingly, most of the players above were taken in the first round. The good: Minnesota has hit on a lot of its top picks. The bad: The Vikings don't have a good history of finding gems later in the draft.
Minnesota did get a find in Tarkenton, though, who is the best third-round pick in NFL history, at least according to Weighted Approximate Value.
For reference, here are the top picks in each round from 1-7, with anyone from round 8 or on (the NFL moved to a seven-round draft in 1994) included in one batch. Since quarterbacks are more likely to have a higher value, we've included the top non-QB as well, when applicable. Also, when an AFL player was the highest-rated, we've also included the highest NFL-rated draft pick in that round.
Round -- Player, AV
1 -- Peyton Manning, 177; Ray Lewis, 160
2 -- Brett Favre, 156; Mike Singletary, 121
3 -- Tarkenton, 149; Terrell Owens & Jason Taylor, 119
4 -- Jahri Evans, 108
5 -- Tarkenton (AFL); Zach Thomas, 118
6 -- Tom Brady, 164; Greg Lloyd, 93
7 -- Bobby Bell (AFL), 103; Tom Nalen, 102
8-plus -- Johnny Unitas, 9th round, 114; Paul Krause, 12th round, 113
Here's the top-five picks by the Vikings in every round since their inception, using Career AV rather than the AV just with the player's time in Minnesota:
Eighth Round Plus
Among active Vikings, Robison could obviously still move up among the fourth-rounders but he also should be aware that Everson Griffen (37 AV) could pass him up soon, too.
Players like Anthony Barr (25), Xavier Rhodes (22), Kyle Rudolph (22) and Harrison Smith (30) have a long way to go to reach their respective top-fives (all were first-round selections, with the exception of Rudolph, a second-rounder).