Okay. That's not actually true. Magic the Gathering (TM) THAT is really the poster child for both getting complex results from simple rules and players coming up with some crazy stuff.
The thing is, while I admire the design of Magic and I respect Wizards of the Coast's business model for getting players' money out of their wallets, I've never been into Magic. The pay to play model has never really worked for me.
Dominion let those of who didn't want to invest in Magic a chance to try out deck building and see how card interaction works. I mean, not counting Blue Moon, Scarab Lords and Minotaur Lords, all by Reiner Knizia :D
(Jeez, I'm setting myself up for not just other games to discuss but other games by Reiner Knizia!)
But a key part of what made Dominion work was the low entry point. (Plus the ability to play with more than two, a wide variety of distinct cards, fascinating interaction of cards, etc) It is really easy to teach folks how to play Dominion.
The basic formula of A: play an action card B: buy a card and C: cleanup by putting your hand in your discard pile and drawing a new hand means you literally have an ABC to teach people. And all twenty-five of the cards that come in the first box are pretty easy to understand.
However, after you get passed the big money strategy, where you just buy coins to buy points, you start exploring how the cards interact with each other. You discover different combinations and learn how cards have different values, depending on what other cards are available.
Dominion embraces both sides of emergent gameplay, complex situations out of simple rules and players coming up with novel, surprising, or even shocking card combinations.
And that is just with the original twenty-five kingdom cards. Every expansion has just add more combinations to explore and discover!
I am also going to argue that Dominion offers a greater degree of emergent gameplay than deck builders likes Ascension that use a random center row. Since you know which ten cards you have to work with in any given game of Dominion, you're able to make more deliberate, specific choices.
Magic the Gathering really helped refine synergy between a wide variety of cards but Dominion helped a different audience explore it.