Yeah, there were eight Mega Man games. They also had Mega Man X, about a different guy named X (the letter). There were eight of those, too. The first Mega Man has a collected version with his eight main games and Mega Man X has one with six of his games on it.
I only played some of those... I think I only played the first Mega Man X and the first five plain Mega Man games. I always liked the variety of the enemies they used. Every game it was something new, interesting, and different to overcome.
There's also Mega Man Zero, Mega Man Battle, Mega Man Legends and some others. Mega Man was in a bunch of fighting games, too. All together, there's probably about 50+ different games featuring Mega Man.

I didn't realize there were so many until I looked it up just now.