I have not played it with only adults for a long time, only with (young) children mixed and parents/family; there are a lot of examples to ruin the game (for me and kids and most adults except 'the winners' (woohoo! I beat some kids at a boardgame!)); one of them (one of the most annoying imho) being that if you pick up (at least) 1 of every monopoly and then refuse to trade/sell unless it's for crazy amounts. So no-one can have a monopoly; then it's just a tiresome waiting game, so people (esp kids, but me too as i'm bored already thinking about it) are going to forfeit or will just buy stuff at stupid prices hoping to get lucky (which they won't usually). You don't need to do that and you can just 'sit it out' but it ruins the game element completely. Ofcourse this requires luck with the dice but more often than not, the monopolies are quite evenly distributed in my experience. It depends what you get, but if you have this hand, then you will probably win by tiring everyone else out (especially because really no-one else cares about winning; we were just wanting to have fun).
> It's like beating you is all that matters to them
It does, which is weird considering this is not actually real life or real money; it's (can be anyway) a nice boardgame on a rainy sunday.
We had a house rule where no trading could happen until all the properties were owned by someone. Created a frenzy and lots of excitement waiting for the last one to be rolled on.
I think there are times for both kind of play. It's annoying when people only play one kind of way. It's like beating you is all that matters to them.