If you can't imagine trading with another player in a way that would give that player a Monopoly, you haven't exhausted the strategy space of Monopoly, a seminal game in the history of board games that all 3M/German/Euro-style strategy games of today owe a debt to.
I'm going to stop because I feel like I'm falling into a bizarre habit of only commenting on HN when Monopoly is brought up negatively:)
edit: if there's an obvious, unstoppable winner at any point in any game, you are allowed to stop playing.
No, I wouldn't, except if it gives a (more valuable) monopoly to me.
You talk a lot about strategy, but what strategy is that? Afaict any strategy in Monopoly is "static", i.e. prefer orange properties, then the second set in each street, etc. That is, the boring sort x)
Play by the rules and the game is very fun with a lot of strategies.
It forces every property on the board to be owned with just a few times around the board.