There are huge differences between Rollins and Granderson. While I agree Granderson is somewhat underrated, you are wrong to pick your fight by comparing to Rollins.
1) Rollins is a gold-glove shortstop and the leader of his team, and managed to play every single game. Granderson is an outfielder and trust me, the Tigers would survive without him.
2) Sure it is easier for Rollins to hit Homers in his park, but it is damn near impossible to get triples in that tiny park, so that evens itself out.
Lets Compare Numbers
Doubles they each had 38
Triples:
Rollins: 20
Granderson:23
HRs:
Rollins: 30
Granderson: 23
RBIs:
Rollins: 94
Granderson: 74
SB:
Rollins: 41
Granderson: 26
Strikeouts (Big One)
Rollins: 85
Granderson: 141
With similar averages, it is easy to see why Rollins is a MVP (as in Most Valuable Player to his team) and Granderson is just another important piece of a damn good Tigers team. The differences in the NL and AL are amazing... Granderson may be MVP worthy in the NL at some point, but the AL is just stacked. You definitely picked the wrong fight here.
To add on, my list of most underrated players:
1: Hanley Ramirez
2: B.J. Upton
3. Carl Crawford
4. Mike Lowell
5. Granderson