Amiga 1000 was released in mid-1985, although I think few units were shipped before 1986. Amiga 500 was 1987 - same year as VGA, its little brother MCGA, and the Mac II.
Not sure when VGA would have been considered mainstream... 1989 maybe? Mac LC was 1990, so probably before that.
VGA and Mac color were better for most practical things. Square pixels and far fewer resolution/flicker/color tradeoffs.
> Amiga 1000 was released in mid-1985, although I think few units were shipped before 1986.
It was announced on July 26th, 1985 at Lincoln Center with Andy Warhol painting Blondie (Debby Harry) live on-stage (a demo which was re-created at the Computer History Museum this past Summer as part of the Amiga 040th celebration). But you're right it wasn't commonly available until the late Fall. I managed to get mine at the end of November.