Originally released on the Capcom Store, the soundtracks of Mega Man and Mega Man 2 are now available on iTunes. Released in two volumes, each album contains music from both the NES and PSOne releases of the two games.
Volume 1 will contain the music from the first Mega Man while Volume 2 holds the music from Mega Man 2. The iTunes release seems to merely serve as an alternative to purchasing the music from the Capcom Store. In fact, the only difference between the releases on iTunes and on Capcom's online store are the album's title and a slightly higher price point from iTunes.
If you want more Mega Man tunes, they can be found on the Capcom Store which range from the first Mega Man up to Mega Man X4.