For me, it was when I was a kid and finally beat all the Robot Masters, and thought that the game was over, but then even MORE levels opened up and I thought "Yep, this is pretty much greatness!"  Yo this game is hot for real....

For me it was the Quickman level.  That stands out in my mind as one of the trickiest and most memorable levels of the 8bit era.
I'm looking forward to Mega Man 9 for sure.

When I put the game in my NES and the music started playing.

"For me it was the Quickman level.  That stands out in my mind as one of the trickiest and most memorable levels of the 8bit era.
I'm looking forward to Mega Man 9 for sure."

"When I put the game in my NES and the music started playing."

The Title Screen.

hehe Seriously, I'm not sure but it was probably Clash Man's level or maybe Quick Man's (LOVE that music) But it was definitely Mega Man 2's level design that made me have it as my favorite MM. I love this game and glad I finally beat it a few weeks ago on my 360 on Mega Man Anniversary Collection.

Actually, just the title screen with the swooping camera up the building was enough for me :)

I know what you mean. Best title screen ever! I love how Mega Man's helmet appears on his head when you start the game.