Games that look terrible/generic shovelware but are actually amazing to play.

[Kaunisto]

I may be biased as fan of the comic, but I loved Rogue Trooper. (Played the original on PC, haven't played the Redux remake.)
It may look like just another scifi shooter but I enjoyed it more than any other such, perhaps save Halo. (I'm talking only about single player.)
The system of "buying" ammo and health with salvage is genius and you can play in different ways: go Rambo, snipe, sneak, throw grenades/mines or use various gimmicks.