Here are some unlockables in the game

Vectorman: Have a saved game file from Sonic Heroes or Sonic Mega Collection Plus on your memory card to unlock Vectorman. Alternately, accumulate a total of five hours of game play time in Sonic Gems Collection.

Vectorman 2: Accumulate a total of seven hours of game play time in Sonic Gems Collection and play Vectorman at least once to unlock Vectorman 2.

SONIC R UNLOCKABLES
Course: Radiant Emerald: Finish the 4 main courses in first place

Dr Eggman: Finish Radiant Emerald in first place

Super Sonic: Get all the 7 Chaos Emeralds, highlight Sonic and press Down

Metal Sonic: Get the 5 tokens in Resort Island, finish in 1st, 2nd or 3rd place and defeat him

Metal Knuckles: Get the 5 tokens in Reactive Factory, finish in 1st, 2nd or 3rd place and defeat him

Doll Tails: Get the 5 tokens in Radical City, finish in 1st, 2nd or 3rd place and defeat him

Eggrobo: Get the 5 tokens in Regal Ruin, finish in 1st, 2nd or 3rd place and defeat him