I don't play computer games all that much, other than those which allow you to vicariously murder your friends in interesting ways over beer and snacks. I do dabble in solo games, but my tastes in that particular hobby generally run to the obscure, arcane, and old. My main areas of interest are interactive fiction (particularly Inform 7) and roguelikes, which is pretty much the fringe of the fringe, I think, when it comes to the gaming industry. Europa Universalis II and the occasional nostalgic blast at Civilization II or III is as close as I get to the computer gaming mainstream.
Very occasionally, though, I hear about a game from somebody or other, get my hands on it, and it takes over my life for a few weeks. I'm in the middle of one of those periods right now: I only got three hours sleep last night because I was up until 4am at my computer desk, and it's all Crusader Kings' fault.
Crusader Kings comes from my favourite game company, a gang of Swedish megalomaniacs known as Paradox Entertainment. In common with all their games, its scope is incredible - real time strategy which models every single day between 1066 and 1453, in which the player takes on the role of a noble family in Europe (literally any noble family - be it William the Conqueror's, the Duke of Gwynedd's, the chief of the Lithuanians', or the Count of tiny Caithness') and tries to guide that family and its descendants to glory.
What I like about it are its role playing aspects. The thousands upon thousands of individuals generated at the start of play are all unique and many of them - the countless courtiers who attend on the noble families - are random each game. All the characters have sets of statistics and defining characteristics like 'tough soldier', 'naive puppetmaster', 'club-footed', 'leper', 'modest' or 'generous'. They have friends, rivals and bitter enemies. They are related to each other - spouses, parents and children, cousins, nieces, nephews, courtiers and lieges. They seem real.
Stop me if you've heard this before, because the game really plays and feels like I always thought the D&D campaign setting Birthright should have done. Computer roleplaying games are almost always terrible, in my opinion - linear and repetitive and in actual fact the very antithesis of what an rpg is. But Crusader Kings is the game I've found which has come closest to bucking this trend and which can be termed an actual electronic, solo role playing game - completely non-linear (because of the literally hundreds of options you have when choosing your starting noble, and the lack of scripted events) and without the shackles that, for example, those godawful Final Fantasy games have. (Your character will fall in love with that character. Your character will fight this big bad guy.) To illustrate: in my current game as Bohumund, Count of Chester (who has since died - I'm now continuing as his 14 year old son) I married off my 16 year old son to the 43 year old daughter of the Count of Shrewsbury in order to cement our relationship, and the next month tried to have the old swine assassinated so I could press a claim for inheritance. That failed and I had my ass handed to me (I believe this is the term the kids are using these days) by our mutual liege, the Duke of Norfolk, and his vassals. I've never encountered that sort of freedom in a computer game before.
It really makes me want to play Birthright. The problem with Birthright, though, was that you could never have enough people involved. Four players meant four domains, which is all very well - but what I always wanted was exactly what Crusader Kings provides - thousands of other players with which to interact. The problem with Crusader Kings, of course, is that you're dealing with an AI, which will always eventually succumb to human creativity and be beaten. What's needed really is a kind of gargantuan Birthright PBP game involving every single player under the sun. I doubt it could be done, although I suppose birthright.net might be the place to start.