We talk a lot about minor league numbers around here, and I think we consider league-context, but it seems we only consider them in an abstract kind of sense.  I was thinking about this in partucular in regards to Brandon Wood, who put up such ridiculous numbers that they are hard to keep in context.  Here are all the full-season league average OPS numbers:

Florida St - 260/329/385 - 714
Eastern Lg - 259/327/398 - 725
Midwest Lg - 260/336/389 - 725
South Atl. - 261/336/393 - 729
Southern Lg- 266/339/393 - 732
Carolina Lg- 262/339/405 - 744
Texas Leag.- 270/335/412 - 747
Intern. Lg.- 270/337/423 - 760
Pacific Coa- 278/350/442 - 792
California - 286/357/451 - 808

You can see here how extreme the PCL and the California League's are.  The difference between the FSL and the 3rd most hitter friendly league (the International League) is 56 points of OPS, the difference between the International League is 68.  Here are the minor league OPS+ numbers for some top prospects.  For players at two levels, like Howie Kendrick, the first number is at the lower level and the second at the higher level.  (I only did this for when a player had at least 100 PA's at a level)

player - OPS+ (league)
Stephen Drew - 151/94 (cal/sou)
Hunter Pence - 146/116 (SAL/car)
Andy LaRoche - 144/111 (fsl/sou)
Rickie Weeks - 137 (PCL)
Brandon Jones - 116/90 (SAL/car)
Jeremy Hermida - 133 (sou)
Travis Denker - 133/78 (SAL/FSL)
Delmon Young - 132/99 (sou/int)
Billy Butler - 131/118 (cal/tex)
Howie Kendrick - 131/129 (cal/tex)
Brandon Wood - 130 (cal)
Matt Kemp - 129 (FSL)
Conor Jackson - 128 (PCL)
Dustin Pedroia - 126/97 (eas/int)
Chris Young - 126 (sou)
Felix Pie - 123 (sou)
Edwin Encarnacion - 123 (int)
Prince Fielder - 121 (PCL)
Lastings Milledge - 112/120 (FSL/eas)
Carlos Quentin - 119 (PCL)
Carlos Gonzales - 119 (mid)
Daric Barton - 112/119 (cal/tex)
Andre Ethier - 118 (tex)
Kendry Morales - 118 (tex)
Edgar Martinez-Esteve - 118 (cal)
Russ Martin - 117 (sou)
Andy Marte - 116 (int)
Matt Moses - 116/90 (FSL/eas)
Ronny Cedeno - 116 (PCL)
Nick Markakis - 115/137 (car/eas)
Curtis Granderson - 115 (int)
Corey Hart - 115 (PCL)
Brian McCann - 114 (sou)
Delwyn Young - 114 (sou)
Denard Span - 114/96 (FSL/sou)
Elijiah Dukes - 114 (sou)
Yunel Escobar - 114 (SAL)
Joel Guzman - 113 (sou)
Tony Abreu - 113 (FSL)
Javier Herrera - 113 (mid)
Jeff Francoeur - 111 (sou)
Marcus Sanders - 111 (mid)
Adam Jones - 107/110 (cal/tex)
Brian Anderson - 109 (int)
Chin-Lung Hu - 109 (FSL)
Neil Walker - 108 (SAL)
Ryan Harvey - 108 (mid)
George Kottaras - 106/111 (cal/sou)
Eric Aybar - 106 (tex)
Jeff Mathis - 106 (PCL)
Ian Stewart - 105 (cal)
Blake DeWitt - 104 (SAL)
Ian Kinsler - 103 (PCL)
Josh Barfield - 103 (PCL)
Eric Duncan - 101 (eas)
Reid Brignac - 101 (mid)
Alberto Collapso - 101/100 (tex/PCL)
Kurt Suzuki - 101 (cal)
Joaquin Arias - 101 (tex)
Hanley Ramirez - 99 (eas)
Greg Golson - 98 (SAL)

I think this can help enlighten us to certain prospects hitting-relative to league.  For example, Brandon Wood had a OPS+ of 130, which clearly puts him among the top hitters in the minors, but Matt Kemp, Billy Butler, Chris Young and Dustin Pedroia all put up similar OPS+ numbers, so its not as if he towers above everyone else.  Of course, position, park, and age, as well as scouting reports should also factor in for judging prospects.