Sexual compatibility is important and is deffo a factor that should be considered when entering a relationship...
If you can't provide for your other half or vice versa, then things may become a little gloomy.
The sex doesn't have to blow your mind, but it should be good.
Personality compatibility would be the most important though, as good sex isn't going to keep a relationship going forever.
p.s. I think your picture doesn't tie in with the question. Are you implying that couples of the same sex have sexual compatibility issues? They really don't.