TRB% - MKG 12.5, JG 9.1
AST% - MKG 9.0, JG 8.2
BLK% - MKG 2.7, JG 1.5
Both are career 47% shooters from 2 point range, have a similar STL% and similar PER's (though MKG is a bit better). Green is obviously a better outside shooter (and is slightly better at the line), but that is more his game than MKG who doesn't shoot hardly any three pointers.
MKG is in his 2nd year on a bad team. JG is in his 6th year and has generally played with much better players, better coaches, and better situations on the whole.
I think you guys are kidding yourself into think Green is the second coming while MKG is terrible. Green is a better player at the moment (and he should be), but in a year or two he won't be and pretty much every year after that. Trading JG for MKG straight up is a steal for Boston.