Not nearly good enough if you ask me, considering people still think to this day that he survived.
Depending on how someone BS's it, there CAN be convincing arguments that he IS alive thanks to ZX. Honestly, I think him gettin' blown up in Z4 was one helluva way to kill off the one that can't be killed.
I thought X5 was pretty damn good and the best of them. X7 wasn't BAD, but compared to the rest of the series, it doesn't hold a candle. X8 was a bit better at that, and the whole recolor argument is true, but probably done so, so that they didn't have to make several different designs that could be 'swapped out' with one another since you could equip different parts rather than the whole suit, and using all of the parts of the same 'set' unlocked a new set of abilities. They could have done better, especially with the Ultimate Armor (was CM released before or after X8?), but for the most part, it was an interesting idea that I didn't mind too much. It seems as if in general the power up system used in the entire series of games just sort of fails. Without ranting, it seems as if there's no real point in using the weapons you get from boss'. They're supposed to be power-ups, not downgrades for your regular weapons. X8 did wonders to Axel though since he somehow ACTUALLY differed from X
Different set of weapons, changed his gun for each one that (for the most part) shot a different 'bullet' making things a bit more interesting, and the copy ability thing was done better.