>I remember Mega Man X putting up some considerable resistance (in fact, i never beat Sigma), though i haven't played it in years

I never got into the classic series - I only beat Mega Man X. Sigma definitely gave me some trouble at the end, and also took me a while to get the Hadouken. Worth it tho, even if I only got to one shot a couple bosses with it.

The slow pacing of the classics compared to how fast X was kinda turns me off, but maybe I should give it a go sometime. I also tried Zero, I think I'm around 25% thru that. (´ー`)