Here is the full list of all 26 NBA JAM achievements worth 1,000 gamerscore. It takes around 35-40 hours to unlock all of the achievements on Xbox 360.
Win 10 online ranked matches
Face the hidden boss after Classic Campaign with a team from each division in the Western Conference
Face the hidden boss after Classic Campaign with a team from each division
Win an online ranked match
Win an online ranked match while leading after each quarter
Face the hidden boss after Classic Campaign with a team from each division in the Eastern Conference
Defeat the hidden boss after completing Classic Campaign
Make 5 layups in a row without getting blocked
Win a game with a layup buzzer beater
Beat Backboard Smash in under 2 minutes
Defeat the Pacific Division Legend Team in Classic Campaign
Defeat the Southeast Division Legend Team in Classic Campaign
Defeat the Southwest Division Legend Team in Classic Campaign
Beat the CPU by doubling their score in a Classic 2v2 or Remix 2v2 game
Beat the CPU by tripling their score in a Classic 2v2 or Remix 2v2 game
While losing by one point, go up for a game winning dunk and have time expire. You lose!
Break the backboard in a Classic or Remix game with an alley oop!
Defeat the Central Division Legend Team in Classic Campaign
Defeat the Northwest Division Legend Team in Classic Campaign
Play an online ranked match
Win a Classic or Remix game without letting the opposing team score
Score 50% of your team's points while only shooting three pointers
Hit a buzzer beater while on fire
Keep yourself or your teammate on fire until it exhausts by making 5 or more unanswered baskets
Defeat the Atlantic Division Legend Team in Classic Campaign
Defeat Beastie Boys in Remix Tour