I've been playing Mega Man games for almost 3 decades so allow me to dissect 2 of my favourites in the entire series.
What better way to start than with how these classics play? For starters, they're extremely similar as you run around as the blue bomber while shooting your Mega Buster at pesky robot enemies and jumping through tricky scenarios. One thing that's cool about Mega Man 2 is that it features a weapon that you can charge up in the form of Heat Man's Atomic Fire. Unfortunately, Mega Man 3 doesn't have any similar weapons. However, Mega Man can slide in it which is quite handy and he also has a delightful pup named Rush who replaces his generic numbered items from Mega Man 2. Needless to say, Rush is awesome, especially in Mega Man 3 considering it's the only mainline Mega Man game where you can freely control Rush Jet. Rush Marine and Rush Coil are pretty cool, too. Because of Rush and the ability to slide, Mega Man 3 has slightly better gameplay than Mega Man 2.
Both of these games feature amazing 8-bit soundtracks that have stood the test of time. Dr. Wily Stage 1 from Mega Man 2 is quite possibly the greatest tune that you can find in the NES library while the Robot Master stages boast incredible music, especially in Metal Man, Quick Man, Flash Man, and Wood Man's levels. Of course, Mega Man 3 is no slouch with phenomenal Title Screen music and top-notch tunes in Magnet Man, Hard Man, Top Man, and Snake Man's stages. All of that being said, I'll gladly say that Mega Man 2 has the better music but only by a slight margin. Dr. Wily Stage 1 definitely tipped the scales in its favour.
Mega Man 2 and Mega Man 3 have very different stage designs. Generally speaking, Mega Man 3's levels are longer and Mega Man 2's feature more memorable moments. Who could forget the super-fast death lasers in Quick Man's stage or the ceiling spikes in Bubble Man's underwater level? On the other hand, Mega Man 2 also features some very frustrating parts like the highly irritating Boobeam Trap boss and the part where you have to hop between blocks as the Mecha Dragon chases then fights you. Mega Man 3's stages are lengthy, challenging, and look absolutely fantastic. Sure, there aren't as many memorable moments but the challenge feels much fairer. Plus, there are more stages in Mega Man 3 considering you have to beat 4 of the stages again which now feature all 8 Robot Masters from Mega Man 2 via the devious Doc Robot. Seeing as it's a much longer and more balanced experience, Mega Man 3 wins here.
Robot Masters and weapons
This is one tough category. First of all, Mega Man 2 has iconic Robot Masters such as Metal Man, Wood Man, Air Man, and Bubble Man as well as incredible weapons like the immediately gratifying Metal Blade, handy Leaf Shield, fast-paced Quick Boomerang, and undeniably cool Crash Bomber. Meanwhile, Mega Man 3 is home to Gemini Man, Magnet Man, Snake Man, and Hard Man and has the sneaky Search Snake, homing Magnet Missile, deflecting Gemini Laser, and the boomerang-like multi-directional Shadow Blade. They didn't take as many risks with Mega Man 3's assortment of bosses and weapons as Mega Man 2 featured a weapon that could stop time in the form of Time Stopper and a deadly ceiling during the boss fight against Bubble Man. Because of that, Mega Man 2 wins here but only by a hair.
Both Mega Man 2 and Mega Man 3 are timeless classics that are near and dear to me but if I had to pick only one, it would be...
Winner Mega Man 3
Although Mega Man 2 is a much more iconic game and was many fans' introduction to the franchise, Mega Man 3 remains a refined and worthy sequel. Mega Man 2's music is highly memorable and it definitely took more risks with its stages, bosses, and weapons yet Mega Man 3 managed to bring the series to a whole new level with innovations such as Rush and its level of challenge that rarely feels unfair. In the end, no matter which one of these classics you prefer; you're right! They're both amazing.
That's just my opinion. Agree? Disagree? Vote now!