Because they're so different. James Caan and Billy Dee Williams WERE Pic & Gale. These two new guys, well, they just don't cut it. It'd be like re-casting "Star Trek" with total unknowns as the Enterprise bridge crew. Oh, wait. That already happened, and IT actually worked. This remake, however, didn't.
The main reason the original "Brian's Song" was so good was the way that Billy Dee Williams (Sayers) & James Caan (Pic) interacted, with Pic bouncing racist remarks off Gale left & right. This new, PC version waters the racism down almost to the point of non-existence.
Also, scenes that made the original so funny were completely omitted; for example, early in the film, the Piccolos & Sayers were at a pizza parlor, & Brian described a play gone wrong, ending with, "So, anyway, all the linemen go this way, and it's like I am lookin' at a team portrait of the Los Angeles Rams....Hey, Deacon! Merlin? How's the family, Rosie?" Then Gale pipes up, "It's like, I'm roomin' with a colored player again!" Again, I'm sure this scene was omitted due to its racial undertones, but it took away from the humor of the film.
I found this new version to be much darker, focussing more on Brian's illness and the consequences than on the relationship between he & Gale Sayers, which was the main thing that made the original so special. If you can find the original on VHS or DVD, get it. But, stay away from the remake.
