Great topic!
I have to disagree with "Out of this World" being better on the Genny. I love the SNES version, but the Genny version seemed difficult to control. I could never get the jumps right on the genesis. Maybe the timing was different, but I just couldn't get the jumps right.

Also, I am shocked that "Rock'n Roll Racing" has more tracks. I LOVE that game on the SNES. I never knew about the difference on the Genesis so I am going to test it out tomorrow. Great tip, thanks for the heads up! RocknRoll and Micro Machines are my top two racing games on the old systems. I even got all the Micro Machine games on the Mega Drive that never got released over here.(Like Micro Machines 96, Micro Machines 2, Military Machines, Skid Marks)