Mega Man 3, for me was the best game in the original series. They introduced the dash/slide, giving some clever level designed to be added in the game. The good soundtrack was kept, almost as good as the one from the 2nd game and the bosses, as well as levels received some great improvements on their design. The formula was kept, having you choose which level to go, stealing weapons for the bosses and using them to kill another bosses as a weakness. Making you face all of them in the end again.
We also had our first look at Rush, one of the coolest companions in gaming.