Well, defense is a strong word, as Monopoly is not really that great of a game. On the other hand, I don't think it's quite as bad as some people claim. It's a negotiating game that relies on a lot of luck.
First, I'll address what I feel are valid criticisms of the game.
Swingy: Hoo boy, is it ever! Player A could roll well enough to land only on the card spaces without paying any rent, while Player B unluckily owes rent for hotels on Park Place and Boardwalk. If you thought that missing your Familiar in Dominion was bad, imagine when you cannot buy any properties because the other players bought them first.
Kingmaker: There are very few restrictions to what constitutes a trade in Monopoly. As such, you can see some wildly skewed trades. If Player A is upset at Player B, then he may offer to sell Boardwalk for $1000 while only $500 to Player C. Of course, there are tactical reasons to skew the prices, but this complaint is about arbitrary sale prices. Even worse, if Player A is a ruthless slum lord and Player B is on the losing end and ready to enter Player A's gauntlet of hotels, Player B can choose to sell off his property to Player C for a ridiculously low amount before getting knocked out. Now, a mediocre Player C suddenly has the capital to take on Player A.
Strategy-lite: In Dominion, you can look at the kingdom layout and choose to focus on a Double-Jack strategy or a Gardens strategy. This is nigh impossible in Monopoly. You don't really start off thinking that you'll grab the green monopoly or all the railroads. That's not always true, since you could devote your resources to trading for the entire orange set, but if one person already has the set, will it be worth it to trade for it? It's almost like planning a strategy for electric football.
Boring for Losers: In general, I wrinkle my nose at games where someone can be knocked out and made to twiddle his thumbs while everyone else has fun. This even applies to my cooler games like Robo Rally. Although, sometimes it's a blessing to be knocked out. How many multi-player Dominion games do you just wish would end because you got shafted?
Then there are criticisms that I feel are not deserved.
Tactics-lite: While I agree that Monopoly is not a strategic game, there are plenty of tactical opportunities. You cannot determine where the dice will take you, but there are actually a lot of decisions to make. You may choose to get out of jail as early as possible so that you can buy up the remaining property, or you may stay in jail and collect rent from others while taking no risk yourself. You can choose to buy more houses before a player rolls the dice, banking on the possibility that he'll land on one of those properties. And let's not forget the trading. How much should you sell that property for? What will the other person gain in the process? If that property you want will complete a monopoly, then expect the seller to ask for a hefty sum. Is the amount you're willing to pay going to be covered by the subsequent rent you will be collecting? Even the timing of the trade is important. If you have a chance where you gain a monopoly on orange while your opponent gets a monopoly on red, you may want to wait until your piece has cleared the red spaces before making that deal or you may find yourself paying outrageous rent that prevents you from developing your orange monopoly. Despite some complaints, this game is not determined solely by the dice. There is a lot of luck involved, but the skill in the game is your ability to weather that luck.
Too long: Really, this is the most fallacious complaint I've heard. I've run some Monopoly tournaments, and the official tournament length is 90 minutes. A lot of games conclude in less time than that. Usually, games run long because of weird house rules or rules omissions. Some examples that I've seen:
- Money is not taken out of the game: Some people place Income tax and Luxury tax money in the middle of the board, to be picked up by landing on Free Parking. These spaces serve a purpose of removing money from the game. Sure, you have Go to give you more money. Generally, that evens out a bit. Also, buying and upgrading property is a way to remove money. If you don't remove money, then you have fat cats with large bankrolls throwing money back and forth. There is no tension in the game.
- Money is added to the game: Who invented the concept of putting $500 in the middle of the board for anyone to pick up when they land on Free Parking? That person has no business naming house rules. This makes the previous bullet even worse. Even if people do lose money, they can gain it back again with this rule. The fact that it's $500 (it's usually $500) makes an already-swingy game even swingier. I refuse to play Monopoly with this house rule in play (or most any house rule).
- Not auctioning properties: Most likely, the average Monopoly player does not realize that every property is sold once it's landed upon. If the person landing on it doesn't want to buy it, it goes to auction. The sooner properties are put into circulation, the faster the production. This results in people losing money sooner.
Ignorance of the Public: I'm sure everyone has had the moment when he explains to family or friends that he likes to play board games and the response is, "Oh, like Monopoly?" It can be daunting. After all, you engage in some pretty complex and deep games, and this person just reduced it down to something as basic as Monopoly. It invokes rage in many a board gamer. This isn't Monopoly's fault, though. If your favorite band has a front man who happens to look like Hanson, do you hate Hanson because people keep comparing your band to them? No, you hate Hanson because they suck. Likewise with Monopoly. I can understand someone disliking the game for being too swingy or a giant kingmaker scenario, but direct your ire at the people who don't know better rather than the game. Actually, such a conversation can be an opportunity to redirect that ire into a moment of explaining the array of awesome games that you play.
I'm sure some people will disagree. I'd love to hear those points. Like I said, it's not a great game that requires huge amounts of planning, but it does require some thought behind your decisions. I won't place it in my Top 10 List or anything, but it does seem to get more gripes than I feel it deserves.