is a great BG newbie game that scales well with 2-4 players and it plays relatively quickly. My only caveat is, you really HAVE to sleeve your Dominion cards, you shuffle your deck nearly constantly - so if you don't sleeve the almost 400 cards, you will end up with some pretty frayed cards after not so many plays.
If you regularly have 3+ I would say Settlers of Catan
is an excellent introductory board game. Lots of player interaction, good speed and low downtime, lots of wheeling and dealing. It has always been a favorite of mine and it is the game that got my wife into boardgaming! The theme is light and the game is euro-abstract (no warfare, only building) so those are some downsides if he likes more confrontation. There are several expansions once you get board with the stock game, and some of them (Cities and Knights) are quite good. If he likes Rome or US History they have a Catan Histories series now, one called "The Struggle for Rome" and the other "Settlers of America." I've never played them but Tom Vasel, really liked the Rome one
Speaking of Rome, I just ordered a fast paced card game called Glory to Rome that is getting a LOT of good buzz on BoardgameGeek.com. The art style is cartoony and low quality, but the game is supposed to be fun, quick, crazy, and a tad cut-throat. You might check it out.
If your Dad would like co-op games, my friends, wife, and father currently really LOVE the new Defenders of the Realm
co-op fantasy game. It plays a tad like Pandemic, and the rules are a little weird at first, but once you get into it - the game is easy to understand and tons of fun. It scales well with 2-4 players (and can actually be played solo VERY well if one person controls 4 heroes). We like the game because it really feels like you are fighting these evil forces in a battle to save the land. Your goal is to kill these four generals for the Dark Lord, an Undead general, and Orc General, a Demon General and a Blue Dragon. They slowly move toward the center of the board and if they reach it, you lose (and there are several other ways to lose as well) It is a tad expensive, but the pieces are all cool plastic and the board is attractive. We have a lot of fun with it.
Lastly, I would suggest Last Night on Earth: The Zombie Game
. It plays fast, and is a light, tactics-base game of survival in the zombie apocalypse. One group of players plays the Zombies, the others the heroes. We like it as a two-player game, but it can be played well with up to six players. You have all sorts of scenarios to play and they are all very fun. I suggest buying it with one expansion - Survival of the Fittest, as it adds a bit more strategy for the Zombie players, then getting Growing Hunger as the next expansion.
My parents really love Carcassonne, even my mom, but I played it so much I can't stand it. It is a light tile based game, but it is very fast to learn and very fast to play.