I still love going back to re-play X1 and X2. Having a vague recollection of the order I figured out so long ago is satisfying. Also, I rarely ever use special weapons on bosses. I can do most of them with the standard X-buster and take very little damage. I order the stages based on collecting body upgrades instead...which makes the decision of stage order a little bit easier.
I also loved playing Megaman Xtreme on the Game Boy. It had a mix of bosses and stages from X1 and X2...which made me experience them in a different way. Really cool.
I played it on Game Boy Color, but it was one of those backward-compatible black cartridges that would also work on the original black-and-white monochrome Game Boy. I'm absolutely amazed that they were able to replicate the gameplay feel of 16-bit X-series games on an original Game Boy.
To overcome RAM limitations, the game has "autosave" points every few screens. That's super useful on a portable system where you could be interrupted at any time.
After completing the game, you get to play an alternate game with a whole other set of stages and bosses. I think it covers most / all of the bosses from X1 and X2. After completing that mode, you get to play one with all of the bosses and stages.
Now, there are at least 3 different modes to figure out the best order, so that's plenty of replay value for me.