I don't think I really dislike any of the Mega Man series. I've found them all really fun, from Classic to Legends to Battle Network. To me, it's sort of like the way I can appreciate the old-school Mario platformers, the 3D Mario games, and the RPG Marios. They're all completely different in style and gameplay, but all really fun. You can say Capcom doesn't care about Mega Man anymore, but Keiji Inafune had a great love for his baby and made it into a masterpiece spanning several series and generations, and frankly, I think you can see that from the final smash in SSB4.
My top picks would have to be: Mega Man 1, 3, 6, and 10; Mega Man X2, Mega Man Legends 2, Mega Man Battle Network 3 and 6.
I kinda wanna go into why Mega Man 1 was brilliantly designed from the get-go (outside of the magnet bar quirk) but dangit I did that on DCEnygma's stream already and screw you if you didn't watch it. *runs*