Alright, I agree with you completely that ZERO required skill. Didn't play ZX but I did play ZX Advent. I don't like the difficulty gap in that game, easy was a joke, then all of a sudden. Normal is pretty damn hard! Then Hard is really difficult. and EXTREME is downright impossible (Yea Im talking to you BiFrost! and you Prometheus and Pandora double boss battle!)
X4 should have been the end of the series, I agree with that. X5-X8 I dont really agree with that... X5 was just basically a shadow of X4. X6 I can't even defend, NOTHING was something to defend. Its worst than s***. X7 I didn't like the 3D at all. I couldnt see where a f***en hole until I fell in it. The 3D segment was basically just a trial-and-error of finding holes, where the reploids are and finding the quickest way to save them from this terrible game.
Second on X7, when you die, its only the character who DIED that gets full health, the other character was just SOL and had to waste a life just to fully heal Zero or Axl or X. Also that god damn steamroller that follows you trough out the level. Its just soooooo damn tedious, boring, bland, and just down right the perfect example of the poor 3D aspect of trial-and-error. You need to know where he is attacking in the boss fight, where all the holes are in the chase, and all of those god damn mechs and explosive barrels.
X8 Was the best closer, they just took X4 and made it better, some things are worse (like Gravity Antonion's stage). X8 wasnt trying to be a SNES game. that's your misunderstanding. They just got rid of the 3D and improved the graphics. It was in no condition of trying to even TRY to act like a SNES. This could be my ignorance again, but I'm pretty sure that your just looking at X8 wrong.