The 1997 Version is Better
Obviously the cinematography of the 2005 version is higher quality but the main problem with the 2005 version is:
Jimmy Fallon.
He's just not a romantic comedy lead. He's not really handsome, just kind of mediocre looking and he's not a man's man either. His humour just consists of acting like a baby or puppy dog and he's goofy. His relationship with Drew Barrymore seems really forced and not believable.
Colin Firth on the other hand is a ladies man and a man's man. His relationship with Gemmmell is more believable and you can understand how the football gets in the way of it better.
Mack Strong. That's all you need.
The best friend makes the story understandable and flow alot better than Jimmy Fallon's 4 odd friends (Bald Guy, Crazy Guy, Indian Guy, Black Guy).