There are a few easy games for Platinums in my opinion, like some of the PS2 HD Packs such as God of War and Sly Cooper. I need to Platinum Arkham City too, but they seriously went overboard with Riddler Trophies. I tried doing some the other day, it was fun but ultimately I got kinda bored. I have some other games more or less 'waiting to be platinum'd' cause of how simple the trophies and procedures are. Dead Space for instance is upgrade all weapons, use them on 30 enemies (an entire chapter usually works) and then beat the game on Very Hard and with the Plasma Cutter, both of which I did in a single run. It's just I did it on the PC and the PC versions suck.
One of the more tedious platinums is the Assassin's Creed series. II is doable but the feathers are annoying as hell. The later games have you finding too many collectables and also dealing with multiplayer.