Wow a toughie... I'm gonna have to go with story on this one... but only just.
I'll tell you why I chose it over fun.
Max Payne 1 had awesome gameplay with the ability to slow down time and shoot just about everyone. It was great fun. But it also had an awesome storyline. The reason I chose Story over fun is because this is my favourite game, but I wanted to see which was better from MP1, Story or Fun?
*Spoiler Warning* (Just in case you didn't play MP1 and would like to)
When I shot down the chopper by making the radio tower fall onto it, I had finally made it to the end. The gameplay was awesome, but so were the storyboards. It was the LAST storyboard picture that clinched it.
Max Payne (While in the cop car): "Woden was there... in the crowd, standing by the
sidelines. It wouldn't be over till the man with the
patch would say so. He'd say the right words. I knew he
would. He'd better. Woden grinned smugly. It was the grin
of a winner."
Max Payne: That made two of us.
For some reason, it made fall in love with the whole story, because it looped back onto itself (Which I love seeing). And then an awesome line to finish off with. So, by a whisker, for me, Story takes the podium.