Games don't need stories.

[Pyro as Bill]

The humour in Portal definitely added to the game. GLADOS was hilarious as is every character in Team Fortress 2. Still doesn't need a story though.

I've only played a couple of hours of Braid but I can't say I've even noticed a story, just some dinosaur who tells me the princess is in another castle. Awesome music though, nice artstyle too.

Story might make a good game great but I've yet to see it happen. I see cutscenes and dialogue hurt games more often than help them.