I had to choose between Mission Genocide and Mr.Heli, and I went with Genocide.
Smooth movement is important to me, and the minimalistic graphics are somehow charming. Mr.Heli has neat music, but the gameplay in Genocide is more exciting to me. Yes it does tend to get a little boring, but as levels progress it helps. I got to level 3 where things began to get quite interesting.
A lot of the games on the poll has very annoying sound effects that simply ruins the game experience in my opinion. And no matter how impressive graphics a game may have, chunky movement renders great graphics useless in my world.
Xout was also interesting though, but not quite enough.
I've never played Mission Genocide before, but as it looked amazingly much like a C64 game, we searched for a C64 version and found it. Then we played the game on both machines at the same time. They are 99% the same, but the sprites move smoother on the C64 (as they do most of the time), but overall a very neat Amstrad version.