Assassin's Creed 2 is what I'm playing at the moment, and you get a silver trophy for every advancement you make in the story. (That's 15 silver and 1 gold JUST for completing the game.)
The Alien Breed games are also great. The first has 13 silver and 5 gold, while the second has 12 silver and 6 gold. They both have more silver trophies than bronze and are some of the few PSN titles that have plats. Both are $15 and are actually extremely fun.
If you want PSN games that DON'T have plats, check out these.
Blue Toad Murder Files- 12 silver, 7 gold
Detuned- 1 gold, 5 silver (It literally takes 5 minutes to get all trophies.)
Frogger Returns- 3 gold, 1 silver, no bronze. (20 minutes to complete.)
Linger in the Shadows- 5 silver (5 minutes to complete, like Detuned it's cheap and easy.)
Tales on Monkey Island series, 5 gold, 25 silver (only a few hours if you use a guide, but amazing series anyways.)