One good trade* and the game is won.
If you play the "hard mode" rules, where un-mortgaging costs 10% more, and the "free parking" gives you nothing, and every property is subject to auction when the first lander says no, this game can be over in half an hour. Watch the first few turns, while properties form pairs in people's possession. The shrewdest player will bargain the "third" away from the weakest player, and a trade is made. He has just lost—and so has everyone else. For the pay-table for a monopoly (I mean, in rough descending order of value, the Oranges, Light-blues, Yellows, Purples, Reds, or Railroads) is such that, in any case, the monopolist can buy up hotels while everyone else struggles to pay his rent. The remainder of the game is to see how fast everyone sells off their properties, demolishes their buildings, and gives up. Math has never been more entertaining, but trust me, "that guy" can win this game as easily as poker. If that's your thing, you'll love this.
A truly classic pain in the ass
Monopoly is one of the most ubiquitous board games ever made. It's been translated into nearly every language in existence in the last hundred years, every country has its own version, there's collectors editions for everything from Star Wars to NASCAR, and just about every household in America has one shoved in an attic or closet. Every year, McDonalds invites us to clog our arteries in the vain hopes of getting Boardwalk and Park Place. Hell, my house has three copies of the damn thing, including that one with the debit cards instead of cash. And yet, I can count the games actually finished on one hand. Monopoly's mechanics are solid, house rules or no. You just go around the board, buying up property, passing Go, and occasionally getting your thimble thrown in jail. Once the properties are bought up, the human element comes into play, as you try to trade your way into a monopoly (that is, all the properties of the same color). Once you have those, you start building up houses and hotels, in hopes of bankrupting all other players. At least, that's how it's supposed to end. The problem with Monopoly is, it's really easy to get stuck where nobody can do anything but just go around in circles. If you get some players that know what they're doing, they won't willingly give you that one property you need, unless you give them the much better one you have but have no hopes of monopolizing. Even worse, you can get cut out of the loop within the first ten turns if the dice hate you; lose out on the best properties, and you're on a long shoe ride to oblivion. And then there's the biggest flaw: its length. If there's only two or three players, the game is over in about one or two hours at most. But since this is often dragged out at family get-togethers, you can probably expect the full six players. At this point, the game's length skyrockets past the limits of human patience, to where even the Buddha would be tossing the board and f-bombing his grandmother for taking her sweet time rolling. I've personally been locked in games lasting over five hours , and even then we just had to call it. This is even worse when you get that guy who just has to win. Only Twilight Imperium has ever tried me like Monopoly has. Just leave it in the closet.