I started with Mega Man X so I suppose that might be why that series is my favourite. Mega Man Legends would follow close behind with the original series close behind that. I never did play the MM Zero or ZX games though to be honest so I can't really say anything about those.

I do appreciate the original series unforgiving nature and the games are quite well designed, but I just can't put them over MMX or Legends when I look at which series I enjoy playing the most.