Oh, it's certainly one of the more historically accurate historical movies. It presents a reasonable interpretation of the big picture, and has some interesting vignettes.
Longstreet's remonstrance to Lee about how no 15,000 men he's ever seen could take Cemetery Ridge is based on Longstreet's memoirs, which he wrote after Lee's death, and after he himself had become a pariah amongst his former colleagues for becoming a pro-Reconstruction Republican, while they were all promoting the "Lost Cause" mythology and damning him as a traitor and--very much ex post facto--the reason for the defeat at Gettysburg. He had reason to make himself look good, maybe a little better than the facts warranted.
I don't think it presents Buford's fight early on Day 1 very clearly. But, then, neither does Michael Shaara's book.
Still, it's far better than most.
Battle of the Bulge is one big steaming pile of crap.