How can i restore black gloss kitchen cupboard doors?

In a word NO! nothing except re-paint.
Brillo pads and shiny surfaces don't go together unless it's glass. What you did is like cleaning your car with fine sand paper and wondering why scratches appear. Why do you think brillo pads are used to clean dirty saucepans?
To RE-PAINT.
Look up www.plasti-kote.com
click on country name then search for apropriate spray paint and email them for advice.
It's very good paint I currently use the stone paint, undercoat and clear sealing coat for the castles I make in mdf. Brilliant paint and well worth money if you follow instructions and do the job properly.

Bob
January 2011