Guys are actually really easy to buy for. He's probably into some kind of hardware - cars, computers, carpentry, golf, etc. You just have to know what he's interested in and what he hasn't already got.
As for computer games, look on his shelf to see what he'd already got, then list them here for clues from our local "experts" or take the list to a good software store. If you're certain he likes RPG games try
metacritic to find out what's good.