It's something of an anomaly.
I was eagerly anticipating the Virtual Console release of Mega Man 3, a game I treasured as a child and continued to uphold through adulthood. That blessed release finally occurred, and I downloaded the third of Mega Man’s NES adventures posthaste. What I found, however, is that the game is an oddity for a number of reasons and that it has not, perhaps, withstood the test of time as well as its immediate predecessor. It’s still fantastic in its own way, but there are some things you should be aware of.
First of all, Mega Man 3 introduces the slide move, and the level design often makes good use of it, especially in Needle Man's stage. Second, it’s one of the only Mega Man games that eschews traditional elemental-type Robot Masters. This game has complete oddities like Needle Man, Shadow Man, Top Man, and Snake Man, so figuring out the proper boss order can be difficult—were it not the age of the Internet. Third, Mega Man's loyal canine companion, Rush, is introduced with all three of his usual forms: Coil, Jet, and Marine. Level design has improved over Mega Man 2, at least in the main Robot Master levels. Things go sideways after you beat the initial eight, and you’re then forced to revisit remixed versions of four of them, each containing two bosses that embody the “spirits” of the Mega Man 2 bosses. Figuring out the proper weapons to use is even worse here. In Mega Man 2, fire beat wood. But there is no fire analogue here. Instead, it’s Needle Canon.
After that, it’s off to Wily-Land, which features truly evil level design that makes you experiment with your arsenal in brand-new ways. Initially, that seems pretty awesome. Eventually, it drains your subweapons and they do NOT refill between Wily stages. It’s possible to really screw yourself during the later stages if you die and run out of movement powerups like Rush Jet or Rush Coil. This is especially apparent when you're fighting the Yellow Devil (remember him?) and each time you die, you're seriously set back.
So liberal use of Restore Points is recommended, specifically with an eye to your subweapon power levels. Use a Restore Point when your power levels are high.
All in all, Mega Man 3 is a logical evolution of Mega Man 2 but commits to some design decisions that I don’t appreciate. The music is great, the animation is fantastic, and Mega Man 3 avoids much (but not all) of the irritating slowdown that plagued Mega Man 2. I still very much enjoy Mega Man 3, but maybe not as much as I once did.