@Captain:
I never understood how any of the NES games were considered weaker than the others once 3 came around. After 3, they kept the same basic formula and play style, and it was all the same fun. 3, 4, 5, and 6 were basically the same game with different stages and a different gimmick for each one, and if it were any other franchise, that would be a bad thing.
But, since it was god damn Mega Man, fuck-dammits, we demanded that same shit! Because it was fun! And by then it was tradition, too!
5 felt really bland. The level designs, the music, the bosses. It all felt extremely bland. Nothing about it really stood out.
4 and 6, however, were definitely better as they had more memorable bosses and music. Seriously, even Capcom remixed only two tracks from Mega Man 5 in their Rock and Techno soundtracks. Wily got a rock remix, while Star Man got a techno one. All of the other games have at least two within each version.
@Darkstorm:
I think six takes the cake for lame bosses.
http://img.photobucket.com/albums/v284/lord_darkstorm/megamanVI.jpg
The Robot Masters were designed by other people; not Dr. Wily. That and two of them were actually made by contest winners of Nintendo Power (Cloud Man and Knight Man).
If anything, 5 definitely had the worst bosses. Not only that, but their powers did NOTHING. The Mega Buster was a far more reliable weapon than the "power ups" of Mega Man 5, especially in "Proto Man's" and Wily's Castles. Even worse was that Beat was your only sure fire way of beating Dr. Wily without taking forever with the Mega Buster.
That and you have the weaknesses making little to no sense even more so than some of the Robot Masters in Mega Man 4.