LogFAQs > #963046292

X games take more dexterity so you'll constantly be holding and pressing different combinations of buttons. Dash jumping, wall jumping makes you much more maneuverable than the classic megaman games and the design expects you to use it.

The classic games strictly punish you for bad timing and have less leeway for course correction.

The zero series expect you to master the gameplay and punishes you for using the elfs.
In the x games you can play through them and go back feel like you master. It doesn't deprive you of techniques or powerups even though you might not eventually use them. Zero is like you want this you must prove you are worthy first and makes it all about chasing your ranking.