There does need to be middle ground for benefits for playing as 3 moralities. Too often we see that Nuetral is never covered and your choice is either being the best good guy ever or the worst human being ever.
Infamous is good example of this, you have the choice of being evil or a hero, nothing in between. You can try, but even if you somehow succeed in being nuetral you're powers are locked at base level because they are morality rank based. Then there's the issue of balancng the powers, now it's somewhat debatable, but I think the general consencus is that being EVIL gives you the best powers.
And then there's games like the STALKER series which do have a morality system. But you're retarded if you want to be a bad guy, because you don't gain anything by being a murderous asshole except the ability to kill anyone and loot the lack of stuff they'll have in their pockets (not to mention everyone in the Zone will hate you and will shoot you even in areas you're not allowed to have weapons). Then there's being the great guy which, everyone is nice to you, gives you discounts on trading, will come with you to help out in a gun fight, and also give you side quests.
There's no balance.