Chris is right all consoles are pretty much obsolete once they hit the market but thanks to standardization game designers can pull some great looking stuff off.
-Voice chat with friends that live several states away
-Being able to use my video game systems for more than just video games.
-D-bags on Xbox Live that why I only play MP with friends now
-Really short games; if I'm paying $60 for a game I should be able to get more than 4 hours out of it.
-Games that skimp out on single player for multiplayer; some of us gamers want to have a nice balance of both. An example would be Modern Warfare 2 you get a three hour campaign give or take depending on the difficulty then the rest is all MP.