Well, first of all, I agree it was challenging at first, but the key is (and that's the same in most of those megaman games) to fight the bosses in the right order since you get their weapons. It took me a while to figure out which one to fight first but eventually I found out. For all of you who don't want to try every one, ...
SPOILER ALERT: ... try the Bug Boss first, it one of the ones on the left and then the others are possible to be beaten. And espacially at the final battles, you have to use your sliding ability. Because you can slide and shoot at the same time, and if you choose he right weapon, it gets quite easy at the end.
But still, there are a few things you could change:
Shorten the "Die-sequence" or make it "skipable".
Make it possible to skip the capcom screen, because it takes a while, espacially when you fought a boss and can't kill him yet. ( Or even better: If you get kiled, and you want to get to the main menu again, just leave out the capcom)
Maybe you could put some more effort into the design of the bosses :) !!!!!!!!!
I guess there are a million things to add, but I think those are not too complicated and would make the game more enjoyable