Here is the full list of all 49 Create achievements worth 1,000 gamerscore. It takes around 30-35 hours to unlock all of the achievements on Xbox 360.
Collected all 610 Sparks
Used every type of rocket within challenges
Solved 20 player generated Challenges
Placed all types of animals throughout the game
Solved a Contraption-o-Matic Challenge with a contraption built of 40 or more parts
Collected 501 Sparks
Eaten 50 slices of toast
Unlocked Future World II
Attached 50 objects which have string to Challenge objects
Unlocked Outer Space II
Unlocked Family Home II
Used every brush in Paint mode
Unlocked Theme Park II
Collected 284 Sparks
Unlocked Darkworld
Unlocked Pirate
100 balloons burst
Unlocked Urban Sports
Completed a car based challenge after all its wheels had been burst
Unlocked Future World
Placed the Create team's favorite animal!
Submitted an entry to a Community Challenge
Saved a Creation or a Challenge from Free Create
Uploaded a remixed Creation
Uploaded a Creation
Remixed and saved a downloaded Creation
Downloaded another user's Creation
Solved 10 player generated Challenges
Solved a player generated Challenge
Marked the content of 10 different online users as a favorite
Rated the Creation of another online user
Downloaded an EA Pick
Marked an EA Pick as one of your favorites
Marked another user's content as one of your favorites
Unlocked Ancient History
Unlocked The Great Outdoors
50 explosions set off
Collected 100 Sparks
Reached a x20 multiplier in a Scoretacular Challenge
Unlocked Outer Space
Uploaded a Solution
Solved Challenge 10 in Transportopia entirely with Horseshoe Magnets
Driven 2,000 meters in vehicles within Challenges
Unlocked Family Home
Finished five Create Chains on a level
Unlocked Transportopia
Unlocked Theme Park
Solved your first Challenge
Earned your first Spark