My favorites will always be the Zero since they are the only saga that I have played complete but I have enjoyed some X a little of the first battle network and the ZX
TeamZero
Edit
I grew up playing 1 and 2 on a gameboy.
they got me a gameboy in what was 2010 or smth
so nostalgia kinda blinds me but DANMMM I looked up megaman 3-12 and they had some unique game mechanics.
also battle network was crazy, love turn based games