If he's a pretty dedicated gamer, I'm sure he'll enjoy Fallout 3. It's an RPG/FPS hybrid game with quite a lot of depth to it. Although, as I understand it, the PS3 version is probably the worst because there are a few graphical glitches that come up. But it's still a fantastic game nonetheless.
A list of other highly-recommended games:
- GTA IV - An obvious choice for PS3. I'd be surprised if he doesn't have the game already.
- Far Cry 2 - Immense world to explore where you're free to do what you want. Plenty of choices in the way you approach tasks. Lots of shooting action.
- Bioshock - Great story. Atmospheric. Again, lots of ways to accomplish tasks. FPS/RPG hybrid like Fallout 3 but without the expansive world to explore.
- Dead Space - Haven't played it, but apparently it's good. There's my justification.
- The Elder Scrolls IV: Oblivion - Get the "Game of the Year" edition if you can. It has the original plus all the other stuff that's been released and the expansion pack. It's an RPG where you're free to do pretty much anything you want. I don't really know what to say. It's just a great game.
- Metal Gear Solid 4: Guns of the Patriots - Stealth-action game with a pretty cool story like the other games in the series.
- Rainbow Six: Vegas 2 - Tactical FPS with lots of intense shooting action helped by the innovative cover controls. You can unlock a whole bunch of new weapons and other things the more you play.
- Call of Duty 4: Modern Warfare - Again, intense shooting action. Online is where the game is at its best.
You really can't go wrong with any of the games I've listed there. I realise that most the games involve quite a bit of shooting, so if he's not a huge shooting fan I could make other suggestions. But they also happen to be some of the most highly-regarded games for the PS3 (and other platforms where applicable).
And even if he does get a look of disappointment, I suppose you could get some insurance against that if you buy the game from a store like "EB Games" or "GAME". They have a 7 day return policy as long as you have the receipt. Or even better, you could get a gift voucher from those stores and let him choose his own game. But I have to warn you, the newer games I've listed (Fallout 3, Far Cry 2, Bioshock, Dead Space and maybe GTA IV and Metal Gear Solid 4) might cost up to $110.