Not as good as 2 but still great!!
The music is not as good, except for the Snake man level which totally rocks. The sound effect are nice but i don't like the new sound when you hit enemies... it sounded better in Mega Man 2.
Mega Man 3 is one of the longest (if not the longest) game in the NES series. After you have dispatched the 8 robots you'll have to go thru 4 levels which contains two foes from Mega Man 2. After that is completed, you'll be able to do the Dr. Willy Castle levels.
Mega Man fans are usually torn on what is the best Mega Man ever... 2 or 3. I'll have to go with 2 but Mega Man 3 is still golden.