Here is the full list of all 50 SSX achievements worth 1,000 gamerscore. It takes around 30-35 hours to unlock all of the achievements on Xbox 360.
Collect all Gold Race Badges
Collect all Gold World Tour Badges
Collect all Silver World Tour Badges
Survive Whiteout Deadly Descent without equipping pulse goggles (in World Tour)
Survive Rock Deadly Descent without equipping armor (in World Tour)
Collect all Bronze World Tour Badges
Survive Darkness Deadly Descent without equipping a headlamp or pulse goggles (in World Tour)
Survive Cold Deadly Descent without equipping a solar panel (in World Tour)
Survive Avalanche Deadly Descent without equipping armor (in World Tour)
Survive Ice Deadly Descent without equipping ice axes (in World Tour)
Survive Gravity Deadly Descent without equipping a wingsuit (in World Tour)
Collect all Gold Explore Badges
Collect all Silver Explore Badges
Collect all Silver Race Badges
Collect all Gold Gear Badges
Ride with all three Pilots with each member of Team SSX
Earn a Bronze in a Survive Event with every member of Team SSX (in Explore)
Earn a Bronze in a Trick Event with every member of Team SSX (in Explore)
Earn a Bronze in a Race Event with every member of Team SSX (in Explore)
Collect all Silver Gear Badges
Earn your 1st Gold in a Race Event (in Explore)
Collect all Bronze Gear Badges
Collect all Gold Tricky Badges
Collect all Silver Tricky Badges
Collect all Bronze Tricky Badges
Collect all Gold Survive Badges
Collect all Silver Survive Badges
Collect all Bronze Survive Badges
Collect all Bronze Explore Badges
Earn a Bronze Medal on a Trick Event in Explore without landing any Super Übers
Reach level 10 with any character
Earn your 1st Gold in a Trick Event (in Explore)
Collect all Bronze Race Badges
Unlock every member of Team SSX through World Tour (or purchase in Explore or Global Events)
Beat a Friend's Rival Ghost in every Range (in Explore)
Earn a Bronze Medal on a Race Event in Explore without using any boost
Earn your 1st Gold in a Survive Event (in Explore)
Make your first Mod Purchase
Collect all Gold Global Events Badges
Collect all Silver Global Events Badges
Participate in a Global Event in every Peak
Collect all Bronze Global Events Badges
Deploy your wingsuit for the first time (not achievable in Tutorial)
Make your first Board Purchase
Make your first Gear Purchase
Upload your first personal ghost
Rewind out of Death for the First Time (not achievable in Tutorial)
Survive Trees Deadly Descent without equipping armor (in World Tour)
Grind your first rail (not achievable in Tutorial)
Unlock all Game Modes