More info about 20XX:
- Massive item roster means that most games will progress differently. Item shops, loot crates, and challenge rooms will dump all sorts of goodies into your little greedy robot fingers. Provided that you can reach them, anyway...
- There are usually more ways to deal with obstacles the further you get into a particular playthrough. Incidentally, there are also more aggressive traps and enemies to deal with, and bosses you fight later will have additional and more powerful techniques and health, which factors into your overall strategy.
- Co-op mode. Has to be experienced to comprehend. Mega Man Universe? What's that?
- Constantly rotating boss roster every season means that there's more bosses than are shown on initial playthroughs.
- Roguelite is not only implemented in stage assembly and enemy/powerup placement, but you also get to choose whether or not you actually bother to take a boss subweapon (you also have the option to pick a powerup or more currency to use at shops), meaning that even when you don't like a subweapon, you won't go away emptyhanded. Incidentally, since the game tracks things like how often you reject subweapons, the developers usually respond after a given period of time by adjusting the game so that the subweapon doesn't suck.
- Daily and monthly leaderboards for fastest completions of game seeds (everybody gets the same configuration) of varying levels of difficulty. Also regular leaderboards for regular and challenge mode gameplay. Yes, there are also co-op leaderboards.
- Both not-Mega Man X and not-Zero are available to play right off the bat. Also, not-Mega Man X is a cute girl.
- When everything goes right, you will feel like a god. When everything goes wrong, you won't feel robbed because it's very likely that you screwed up and not the game. (If something does go wrong with the game, you can report it and it'll be addressed in the next regularly scheduled patch.)