The Torps

Cooperation: Boardgames are played for mutual fun, there's a sense of friendship while playing (perhaps excluding tournaments) - to the point of letting people take their turn again if they made a mistake or helping them out with suggestions during their turn. Even though it's player-v-player there is very much a Co-op feel about playing boardgames. I find that both World of Warcraft and City of Heroes generate this same feeling (at times) where some players will go out of their way to help you, not looking for anything in return except for enjoying themselves. The same cannot be said for many other games!

Well balanced games: These boardgames seem to be well balanced, even with players of differing skill levels (possibly also due to the friendliness of the players involved). To be fair, there are many many boardgames that do not have lasting appeal, often due to this very issue (being unbalanced). Cue the CS newbs to yell "TEAMS!!1"

Simplicity: For the most part, a new player can be coached in a fairly short time so that they know how to play the game - the finer details can be explained as the game progresses. Some of my favourite computer games are simple, yet engrossing. It's one of the reasons I often prefer Dungeon Siege to NeverWinter Nights (except when in the company of rules-lawyers who can help me in NWN)
The complexity should generally not be in the rules/controls but in the mastering of the game.

Originality? : One thing that was interesting was the lack of 'new' board games - the newest was Catan which is 10 years old, the others were 15-25 years old. Now to be fair this is mostly because we are all old farts who haven't been playing many boardgames in the last 10 years, but I suspect the peak period of originality/innovation in boardgames has long past. Greg Costikyan said some interesting stuff about innovation in boardgames/computergames in his rant at GDC this year, I don't agree with it all but it is worth a read (also at boingboing)

War Stories: One thing that I noticed seems to be true of many games that are engrossing is the war stories that they create. Players like to tell other players about what happened in the game (e.g. Rimmers Risk Story). This is no different to sports stories, highlight reels, etc. Not all great games do this (Tetris stories anyone?) but many do and it's a telling sign that a game has found a permanent home in your head. What was your last gaming war-story ?

Space Hulk War Story from this weeks gaming, by Zaph: "Jon flamed the tile, I rolled a 1 and survived, then he flamed again, and I rolled another 1. Jon then flamed a third time, using command points, and my asbestos bug rolled a 1 for the third consequtive roll! one-in-216!. Bart then stepped in, dropping a flame to kill his own teammate (Jon) to hold back the bug, but this was the turning point in the game and the bugs went on to win on the final turn"