*WARNING - Some Spoilers Ahead*
What can I say that others have not said? This looks astounding, guys - it's clear you put a lot of effort into it. I can only imagine how much of a nightmare it must have been, coding each separate level and creating custom sprites and such. The end result is a beautiful tribute to the NES.
Gameplay is suited to each title as it was back on the NES - to critique each one would be time-consuming and rather pointless. On the whole it was very good, sometimes improving on the old titles a little! No game is flawless, however... not even a compilation of excellent games such as this one. The issues with this one do not lie in the gameplay, controls, the music, the art... No, all of that is great and they work just as I expected them to.
The few complaints I have are (for lack of a better word) "technicalities". I know it took a long time to make this, so don't fret! The issues are real minor. For starters, I know it might detract from the overall "feel" of this tribute a little, but it would be nice if you added an option in the Pause Menu to return to the Main Menu. The Refresh button works but sitting through the opening adverts and such is a bit annoying.
Also, for the slow people out there who need time to figure things out (i.e., me), it would be most appreciated if you let us examine the controls at our leisure on the Pro Wrestling and Punch-Out levels, and let us skip them when we choose. They went by on their own before I had memorized them! I managed Punch-Out fine since I was familiar with the game, but I had never played Pro Wrestling and I had to resort to lame punching tactics to win since that's all I could figure out how to do reliably.
The one other gripe I have is the Level Select screen. This one is REALLY small; after all, I love the tribute to Mega Man and the appropriate level names. It's very nicely done! The only minor problem is that some levels are linked, like Balloon Fight/Pro Wrestling and the two Contra stages - to play one you have to beat the other first, so the whole "choose what level you want to play" thing is kind of negated. I can understand if you choose not to alter it, though, since as it stands right now the Mega Man menu looks really cool, and eight levels fit on it perfectly.
All those text boxes and it starts to look like my rating is a mistake! But I assure you, everything else is beautifully done. The lack of comment on it is because I am speechless; nothing really needs to be said about how great it all is, being able to revisit the past in such a manner! And the medals are numerous enough that I'm still gonna be at this for a while... And, of course, the fact that this was FREE and not store-bought makes it all the sweeter. Knowing that, I can't be too hard on it... especially since it's a wonder to behold. Kudos to all of you!