You don't have to upgrade every two years, there's still a computer in this house with a 5 year old hardware and it can run Bioshock Infinite and The Witcher 2 on high.
If you invest a large sum of money (granted an xbox could be cheaper), then the computer will last years and years and still outperform the garbage Xbox 360 (The failure rate on them is still terrible even with their new "slim") And you can play games that just look so much better and not have to pay a monthly subscription to xbox live.
And the point of consoles disappeared when you had to start installing your games on the xbox hdd.