This is a good topic. A lot of big artists' first songs weren't all that special.
After looking a little. Sade had "Your Love is King" which is a good song but probably not in my top 10 of her songs. Anita Baker had "Angel," which is similar. MJ had "Got to Be There." A lot of other big names started out with songs that most people probably don't even remember or never heard of.
I'm going to go with "Protect Your Neck." It was basically the perfect debut song for the Wu. "Who Am I?" was Snoop's solo debut single, so that's up there too.