Does he already have an Xbox 360 ??? Just so I know if you're looking for PS3 exclusives. From how you word it, it sounds like he must already have a 360 though, ha ha. If he doesn't, let us know because then there'll really be a big pile of games to recommend
Anyways, for exclusive PS3 titles, Pornisteph is right, Metal Gear Solid 4 is a great game. Also, one other game that I think is amazing is Uncharted:Drakes Fortune, it's like a mix of Tomb Raider and Gears Of War and it's VERY well done.
http://www.us.playstation.com/uncharted/ There is one bad thing about it though, it's on the shorter side, but good enough for me to play through it a couple of times.
If he's into shooters, you can pick up Resistance, which is a "greatest hits" title for $29.99, then on November 5th, Resistance 2 comes out, pick that up because it's gonna kick ass