#1 (tie). PlayStation & SNES ~ on the strength of the libraries of each system, picking between them is an impossible task as my answer would change every day.
#2 PlayStation 2 ~ Another console with a great library of games, maybe not a strong as my two number one picks, but still right up there.
#3 Sega Genesis/32x/CD ~ Combined into one console it's just an awesome setup, there is something for everyone.