My brother bought my dad a laptop in January and he's only used it twice, both times when we were showing him how to use it. He says he feels bad for not using it more and that he actually feels disappointed in himself since his other equally aged friends are at least basically competent with PCs. I suggested that he just needs a practical reason to use it, that me and my friends are only "good with computers" because as kids and teenagers we wanted to play games, so I thought gaming would be a nice reason for him to get on it more, in that it can be as complicated or as simple as he likes and can be pretty addictive, as we all know.

He's now 60, so gaming has had no impact on his life outside of watching me and my brother play on the Mega Drive and PS1 when we were growing up. In the past he enjoyed playing Street Fighter II and Mega Bomberman with me and my brother, but the one time he actually seemed to be hooked on something was when he'd suddenly disappear from the living room and we'd later find that he'd sneaked off to play Rage Racer on the PS1. I'd say a more simple game would be good (so not RTS, and nothing with fiddly control schemes like FPS) and probably racing games, at least as a starting point.

My old man loves Silent hunter 3+4 and MS flight sims.

Out of racing games here on GOG I've quite enjoyed Screamer and Flatout.

Screamer is arcade style racing game, quite fun and addicting, though it has been at least 10 years I've played it.

Flatout has multiple game modes from destrution derby to stunts. You can also get the sequal from steam considerably cheap.

FlatOut is pretty fun. The whole "drivers flying out" bit is a bit silly, but the driving and physics stuff is fun. You also get to fiddle with the cars a bit.

My father seemed to enjoy Diablo at some time in the recent past.

Allow me to suggest TrackMania Nations Forever. In case you don't know about it, it's an arcade racing game filled with fun tracks of varying difficulty, a huge online community, a unique approach to multiplayer, a veritable fuckton of free user-made content (especially tracks), and best of all, it's free. It's easy to learn, and might be just the very thing.

Some arcade and flight games usually works for the non-gamers as they are simple to understand. I used to play his flight simulator when I was a little kid for example:
http://www.mobygames.com/game/chuck-yeagers-air-combat

Is he a book king of guy? Then maybe a couple of point&click adventures could be of interest as they are story-driven and easy to play.

Is he interested in cars in general? Then maybe this game:
http://www.gearheadgarage.com/

Can you list some of his hobbies and his personality?

It's not my father, but my grandfather. My father bought him a PC last year and since then, my grandfather has been glued to it playing card games online. :/ Like literally glued to it.

He refused to touch those "darn things" for years, so it's still amusing to see him so addicted when I visit. Still needs help opening his email a year later, but he knows more about playing various card games online than I do. ;)

I've tried to open him up more...sophisticated games, but he isn't having any of that!

Thanks for all the great suggestions so far, guys. I really appreciate it. Well he gets really bored with puzzles and lateral thinking things pretty quickly. He's much more of a hands-on, practical kind of person. He'd appreciate games like Broken Sword for the story but the puzzles would be a huge turn off for him. I can maaaybe see him playing something more like Lemmings since it's a directly applied kind of logic rather than puzzles for the sake of it.

He really likes music and plays the guitar in a casual band with his friends, but I don't think that'd translate into liking games like Guitar Hero very well. Everyone I know that's in a band hated Guitar Hero, everyone I know that likes Guitar Hero has no musical ability. It might seem odd, but there you go. It's probably better to think of it from a "what sort of films does he like?" perspective, and then I'd say that he likes old-fashioned adventure films like Indiana Jones, the older James Bonds, and also Westerns.

Racing games or pinball ones could prove decent time killers, but I don't think gaming is the best thing he could do to feel the computer is useful. At his age and with a serious lack of gaming background, he might do it just to please you, but when left alone, he might just go back to his usual comfortable zone. The trick is to make the computer even MORE comfortable than what he's already used to doing on average.

Maybe a little social networking (much better than sending mail) or web browsing news sites (better than newspapers), or forums of things he's interested in (better than magazines). You could compile a list of websites as bookmarks, be it humor, hobby or even educational to get him reading stuff he likes in just a couple of uncomplicated clicks away.

From there, he could develop an interest in programs that can help him make money, do things around the house or what have you. As for games, the incredible machine comes to mind and Adventure games are also very easy to use, some with a decent story that older folks may like. Plenty of those on GOG.

Forums are actually a pretty niche thing, you know. Apart from myself, I only know one other person in real life who goes on forums - and we're both known as being a bit geeky for doing so. Same as having specific interests that you check up online; the average person, particularly older people it seems, are just happy watching whatever's on TV, taking the dog for a walk, going out at the weekend and so on.

I do appreciate your suggestions and they make a lot of sense for certain people, it's certainly how I use the internet, and it was my initial thought of making the PC more interesting to him. Thing is, he isn't the nerdy or hobbyist kind of guy who buys various "special interest" magazines, he doesn't even like reading novels or anything. While he's actually a quiet, pretty shy kind of person, he said he hated school and only got through it because he was on the football team. Everything else bored the crap out of him.

Puzzle or board games maybe? Various solitaire types, Mahjongg, etc.
Besides that, Moto Racer games have some nice arcade settings, at least that's what I remember.

The only thing my dad will play is Galaga. So yeah, I don't have much to add here.

My dad is actually the one who got me into gaming. The games he used to play before getting bored of the hobby were Doom II, Heretic, Hexen, Blood, Duke 3D, Shadow Warrior, and Heretic II.

Would shooters be completely out of his league? I'm not suggesting half life, which does have puzzles, but stuff like Unreal tournament 2k4, if he's not a motion sickness kinda guy. Not only can you set the bots to be really stupid and slow or incredibly fast and deadly, but once you get a hang of the mouse to aim and arrow keys to run, you're pretty much done. It's all run and gun from then on, with violence and language filters if you like. I know I played the single player for fun and you can set up a match against bots on any map you want at precisely the level of difficulty you feel most comfortable with. I just wonder if he'll have anything against shooting pixels in a noisy fashion.