Portal 2 vs Mortal Kombat - Which one to get?

So I'm a little miffed at the fact that both Portal 2 and Mortal Kombat were given 5 star reviews. How do I know which one to buy now? I mean I could buy both but then I'd have two games to take up all of my time instead of one and I should be drawing or cleaning my room or instead. Couldn't one have been just alright and then the choice would have been obvious? Gosh darn it!