I agree with BT that none of 'em are really all that bad, but here's the four I think are the least fun:
Exile: Wicked Phenomenon - Vic f*cks up the difficulty level, making it more of a chore to play than fun.
Magical Dinosaur Tour - has some neat art but ultimately comes up short on the entertainment half of edutainment.
Sim Earth - it's a decent enough port, I guess, but Sim Earth is bland and boring in all iterations.
Fighting Street - I can forgive only having two playable characters, but the controls kill it, especially when you wanna pull off special moves.